STACK ANNEX 061 9*4 Some Phases in the Development of the Subjective Point of ^Oie^w during the Post- Aristotelian Period VAGNY GUNHILDA SUNNE PHILOSOPHIC STUDIES ISSUED UNDER THE DIRECTION OF THE DEPARTMENT OF PHILOSOPHY OF THE UNIVERSITY OF CHICAGO NUMBER 3 THE UNIVERSITY OF CHICAGO PRESS CHICAGO, ILLINOIS The Department of Philosophy of the University of Chicago issues a series of monographs in philosophy, including ethics, logic and meta- physics, aesthetics, and the history of philosophy. The successive monographs are numbered consecutively with a view to their subsequent publication in volumes. These studies are similar to the series of Contributions to Philosophy, but do not contain psychological papers or reprints of articles previously published. SOME PHASES IN THE DEVELOPMENT OF THE SUBJECTIVE POINT OF VIEW DURING THE POST-ARISTOTELIAN PERIOD THE UNIVERSITY OF CHICAGO PRESS CHICAGO. ILLINOIS Bgente THE BAKER & TAYLOR COMPANY NEW TOBK CAMBRIDGE UNIVERSITY PRESS LONDON AND EDINBURGH SOME PHASES IN THE DEVELOPMENT OF THE SUBJECTIVE POINT OF VIEW DURING THE POST-ARISTOTELIAN PERIOD BY DAGNY GUNHILDA SUNNE B THE UNIVERSITY OF CHICAGO PRESS CHICAGO. ILLINOIS COPYRIGHT 1911 BY THE UNIVERSITY OF CHICAGO Published March 1911 Composed and Printed By The University of Chicago Press Chicago, Illinois, U.S.A. Stack Annex r TABLE OF CONTENTS PAGE I. INTRODUCTION . . . 9 1 . The Difference in Philosophic Standpoint between Aristotle and St. Augustine 2. Indications of Interest in Inner Experience during the Pre- Aristotelian Period 3. Development of Biological Psychology and Realistic Episte- mology by Aristotle 4. Scientific Method Based on This Theory of Knowledge II. DEVELOPMENT OF THE SUBJECTIVE STANDPOINT IN STOICISM . 18 1. Introduction: Social and Political Conditions; Chief Phases of the Development of the Subjective Attitude 2. Attempts at a Theory of Knowledge on a Subjective Basis by the Older Stoa A. Doctrine of Assent with Reference to Sense-Perception a) Zeno's Contribution b) Limitation of Assent through Skeptical Criticism B. Objective Character of the Object of Knowledge: the Con- troversy between Cleanthes and Chrysippus C. Analysis of Cognition on the Basis of Assent: Chrysippus a) Assent Basal in Cognitive Functions 6) Analysis of the Object of Knowledge c) Preconception as a Criterion D. Development of the Subjective Attitude in Regard to Concepts: Doctrine of the \cKr6v 3. Increased Subjectivism in the Middle Stoa A. Social Conditions B. Growth of Introspection a) Increased Psychological Analysis 6) The Function of Reason c) The Criterion; Analysis of Attention 4. The Subjective Attitude Dominant in Later Stoicism A. Social and Political Conditions of Roman Stoicism 5 2067300 6 TABLE OF CONTENTS l PAGE B. Subjective Attitude in Ethics a) Cicero, Transition from External to Internal Control b) Seneca (1) Psychological Analysis (2) Moral Reformation (3) Spirituality in Religion (4) Political Conflicts C. Ethical and Religious Environment of Later Stoicism D. Increased Emphasis on Self-Consciousness a) From the Individual Standpoint: Epictetus (1) Reflective Consciousness (2) Self-Consciousness the Daemon (3) Theory of Knowledge (4) Autonomy of Will 6) From the Universal Point of View: M. Aurelius (1) Cosmic Interrelationship (2) Social Relationship (3) Autonomy of the Spiritual Element in the Soul (4) Self-Consciousness in Religion III. EFFECT OF THE DEVELOPMENT OF THE SUBJECTIVE ATTITUDE ON SCIENTIFIC METHOD ........ 49 1. Introspective Psychology and Inductive Method: Epicurus A. Thought and Sense-Perception as Psychological Processes B. Judgment and Inferential Reasoning 2. Changes in Method of Later Epicureans Due to Advance in Psychology 3. Problem of Attention in Relation to Method A. Practical Standpoint of Pyrrho and Arcesilas B. Analysis of Attention and Scientific Procedure by Carneades C. Analysis of Inference in Theory of Signs by Carneades, Middle Stoa, and Progressive Epicureans 4. Demolition of Deductive Analysis and Formal Scientific Con- cepts by Skeptics A. Destructive Criticism of Scientific Concepts by Aenesidemus and Agrippa B. Criticism of All Speculative Systems on the Basis of Real and Phenomenal and Outline of Method of Applied -Science: Sextus Empiricus TABLE OF CONTENTS 7 PAGE 5. Personal Experience Made Basal in Scientific Procedure by Empirical Physicians A. Early Stages of Empirical Method; Influence of Psycho- logical Analysis B. Value of Individual Experience Admitted and Occult Causes Rejected by Celsus C. Experimentation Based on Personal Observation: Galen D. Scientific Development of Inductive Method by Menodotus; Logical Formulation by Sextus Empiricus 6. Summary Changes in Character of Universal; Importance of Individual Experience; the Nature of a Problem IV. SUBJECTIVE ATTITUDE AS A BASIS OF METAPHYSICS ... 78 1. General Character of the Imperial Period 2. Neo-Platonism, Metaphysics Based on Psychology with the Emphasis on Intellect A. The Rise of Neo-Platonism B. The Soul-Body Relation as a Problem C. Psychology of Mental Processes and Reflective Conscious- ness D. Metaphysical System Based on Psychology 3. Psychology and Metaphysics of Augustine Based on Analysis ofWiU V. SUMMARY 91 I. INTRODUCTION I. THE DIFFERENCE IN PHILOSOPHIC STANDPOINT BETWEEN ARISTOTLE AND ST. AUGUSTINE In St. Augustine's philosophy the starting-point is the same as in the beginning of modern thought, namely, the certainty of inner experi- ence. Not even the Skeptic, says St. Augustine, can doubt sensation as such; moreover, this very experience reveals not only the content that had formed the basis of relativistic or positivistic interpretations, but also the conscious self, the perceiving subject. For Aristotle and his contemporaries, perception was essentially a cognitive process, apprehending the forms of sensible objects without the matter. Such apprehension of external objects was regarded as direct, the awareness as awareness of the objectively real character of things. A mind as such perceiving was foreign to their modes of thinking; the person, com- posite of body and soul, thinks and knows, was their view. There is ample evidence that self-consciousness was recognized by Plato in his theories of sensation; and that Aristotle made a psychological analysis of it as a mental phenomenon, though he utterly disregarded it in his metaphysics and epistemology. In the earlier period, therefore, mind was studied in its manifestations in nature and society; with the close of ancient speculation, the investigation was based predominantly on introspection and the analysis of mental operations of the individual thinker. It is accordingly an interesting inquiry how this change of viewpoint was effected and what were the consequent alterations in scientific method. Though such a development cannot be treated in isolation from the social life, the scope of this paper will allow only most general and cursory references to the social, political, and religious influences affecting the philosophic thought of the post-Aristotelian period. 2. INDICATIONS OF INTEREST IN INNER EXPERIENCE DURING THE PRE-ARISTOTELIAN PERIOD The Ionian philosophers viewed physical reality as a concrete whole; there was no antagonism between human nature and universal nature in either theory or practice. Heraclitus revolted from the conception of the world established by tradition and the theories of teachers, over against which he set up the claims of reason. To the " obscure philos- 9 10 SUBJECTIVE VIEWPOINT IN POST- ARISTOTELIAN PERIOD opher" scientific research was difficult; for he believed there is an idea expressed in things, a meaning which it is the aim of philosophy to bring to light. It seemed to this ontological idealism that the strife and discord discernible in nature, which had been first mentioned by Anaxi- mander, is an expression of a deeper harmony. Thus the notion of illusion developed, because the hidden harmony was regarded as more perfect than the apparent. In this early development of philosophy also, progressive emphasis was laid on the impersonal element in nature till in Democritus the gods were abolished. On the other hand, the system of Parmenides which influenced to a marked extent the thinking of his successors made no attempt to explain or even describe nature, but endeavored to clarify an idea that should be the permanent truth about things. Athwart this philosophic development came the humanistic move- ment of Sophism. The Sophist discovered the world to be himself and hence all inquiry had a personal aim. Doubting any positive knowl- edge of the world of nature, he turned to the more comprehensible life in society. Now appeared the first attempt at a study of mind, which was further developed by Socrates. Thus the Sophists from an indi- vidualistic, and Socrates with his followers from a universalistic stand- point investigated the human mind in its social aspect. Though the distinction between sensation and reason was early made in Greek philosophy, metaphysical interests predominated. All mental processes were conceived as material operations. In its origin Greek psychology was a division of physics or physiology. Cognition was con- sidered a property of the matter composing the human organism. Em- pedocles first touched on the distinction between sensory and physical facts in his doctrine of symmetry and similarity between object and sense-organ. He attempted to exhibit a common element in the various kinds of sense-perceptions but denied any fundamental difference between them and physical processes. Yet from his time on, two opposite stand- points are apparent in philosophy : the assertion or the denial of a funda- mental distinction between physical interaction and sense-perception. 1 In accordance with his physical theories, Democritus regarded thought and sensation as bodily changes because he had observed that both these activities depend on the organism. The distinction between Ao'yos and ato-flrjo-is had already been drawn. Therefore, there must be two regions of knowledge: one dealing with an intelligible world the formation of things from atoms the other with sense-perceptions. All 1 Cf. Beare 294-95. INTRODUCTION II sensations were explained in terms of direct contact and mechanical manifestations of pressure and impact. Thinking was supposed to take place when the soul-atoms are harmoniously united. Thus the difference between sense and thought processes was held to be that of impact versus organized physical movement. So Democritus tried to formulate the principle to which pure knowledge must conform and to state it as a relation of concepts to sense-perception, not in terms of subjective functions but in those of objective contents. It is typical of the thoroughness of Democritus that he attempted on the basis of the atoms to explain the world as perceived and thought out. In the previous systems, the differences between the two realms had been pointed out and made irreconcilable. Democritus tried to give a thoroughly scientific explanation of their connection, that is, of mind and its relations, from the physical side. Plato on the other hand was the first philosopher to demarcate sense-perception from physical reaction by defining sensation as a movement common to soul and body. Here sensation signifies any immediate consciousness, perception including pleasure-pain. He con- tended that sensationalism cannot account for the synthesizing activity of thought and rejected psychological analysis based on physical analo- gies. We find in Plato an opposition not so much between soul and body as between thought and sense one faculty over against another. Against the Protagorean theory that sensible objects possess their so- called attributes only by acting and being acted upon in the interplay of object and sense-organ, Plato insisted that the defects of sense are not in the perceiving subject but in the object, for the particulars of sense are incessantly changing. No scientific treatment of psychological problems is given, though there are numerous examples of introspective analysis unequaled for keenness and subtlety. For the metaphysical and ethical implications of mind as objectified in society viewed from a spiritual standpoint formed the chief subject of investigation. 3. DEVELOPMENT OF BIOLOGICAL PSYCHOLOGY AND REALISTIC EPISTEMOLOGY BY ARISTOTLE The construction of a thoroughly realistic epistemology based on a correlation of physics with psychology was one of the achievements of Aristotle. In accordance with his teleological standpoint he deals in his psychological treatise with soul as belonging to all animate beings. Soul as such he considers a mere logical entity. It is possible to give a purely generic definition of soul as of geometrical figure, but there is 12 SUBJECTIVE VIEWPOINT IN POST- ARISTOTELIAN PERIOD nothing corresponding to it apart from the particular kinds of soul. 1 Aristotle criticizes severely the treatment of mental processes in the abstract as well as the limitation of observations to the human soul. It is the embodied individual that is the subject under consideration. The view of the soul as an entity is vigorously opposed; the soul is simply the eiSos of a concrete living being. It is not the soul that learns and pities; man learns and pities with his soul. 2 And yet Aris- totle speaks of the soul as the subject of sensations, feelings, and thoughts; and the very fact that he so often refers to a central organ apparently signifies a tendency to locate some peculiarly psychical part. Activity is the basal principle of Aristotle's psychology just as motion is fundamental in his physics. His theory implies that a process of the human organism is of the same kind as some motion in the external world. When a movement is caused by the stimulation of the sense- organs, the form of the external object is communicated to the organism. The content of sensation or thought, whether in the sense-organ or in the physical world, is equally objective. Aristotle believed that the assertion of the relativity of perceptions and the denial of the objective validity of sense-qualities on the part of earlier philosophers were due to their failure to distinguish the ambiguity of the terms sensation and sensible thing. "When they mean the actual sensation and the actual sensible the statement [that without seeing there is neither white nor black, without tasting no flavor, etc.] holds good; when they mean potential sensation and potential sensible this is not the case." 3 According to Aristotle the first two stages of cognition, sense-percep- tion and reproductive imagination, 4 furnish the content of common-sense; this same content, regarded as potential, is the passive reason on which creative reason operates. Aristotle received the groundwork of his theory of sensation from Plato. He defines it as the transmission of some stimulus or impression through the body to the soul. 5 In this manner he connects physics and empirical psychology. By means of his physical theories of motion, efficient cause, matter and form, potenti- ality and actuality, he demarcates sensation from physical interaction and explains the relation of sensation to sense-organ, and of perceiving subject to sensible object. In the reception of the form of a thing with- out the matter, object and act are correlative; they can be distinguished logically, though in the perceptive, process they coincide. 6 The par- 1 De An. 413-15, 013. * avTcurta.4 In his treatment of recollection, he speaks of it as a search depending on will, thus recognizing its purposive character. So he also asserted that the distinctions between truth and falsehood made by theoretical reason are generically the same as the objects of pursuit and avoidance of practical reason, good and evil. 5 But this line of investiga- tion was not further developed. Such a position toward will and reflect- ive consciousness was due to the view held of cognition and epitomizes the great contrast between the philosophical attitude at the beginning and end of the post-Aristotelian period. 4. SCIENTIFIC METHOD BASED ON THIS THEORY OF KNOWLEDGE As thought is concerned either with recognition and contemplation of truth or with devising rules for producing results, Aristotle held that science must be either theoretical or practical. The first principle of the former disciplines cannot be proved and the end of the latter can form no matter for deliberation. Scientific knowledge of universals 1 De An. 425, 62; DeSom. 455, 015. 2 2V. Eth. 1170, 029; Beare 289. 3 irdpepyov. Met. 1074, 635. 4 Z)e ^4w. 433, 09; De Mem. 453, 012. s De An. 431 ^10; TV. Eth. 1139, 026. 16 SUBJECTIVE VIEWPOINT IN POST- ARISTOTELIAN PERIOD is based on experiential knowledge of particulars. True perception is possible and its objects actual; 1 the doubts raised in regard to sense- perception are due to the application made of it. 2 The object of per- ception is implicitly universal. "The concrete individual is perceived but the perception is of the universal, as for example, of a man, not of Kallias, a man." 3 Ultimate principles are apprehended by induction in the Socratic sense. For sense-perception gives rise to memory which depends on the experienced connection of facts, whether that of conti- guity, similarity, or contrast, and "repeated memories of the same object to experience; .... and experience leads to the principles of art and science." 4 Psychologically, then, the mind comes by the apprehension of such principles by induction from examples of their truth in concrete cases. But such induction merely makes possible the direct intuition of the implied principles, but does not prove them; for they are not prov- able. 5 "Some first principles are seen by induction, others by per- ception, others by a sort of habituation, and some in one way and others in another." 6 By perception or direct insight the first principles of mathematics are recognized. In more complex subjects, especially the physical sciences, the truth of a proposition can be seen only as exempli- fied in a number of instances. Demonstration or scientific analysis as discussed in the analytics has to do only with middle terms, that is, with causes in the theoretical sciences and means in the practical. At each end of this process recourse must be had to immediate insight whether sensuous or intellectual. 7 The instrument for getting at mediate propositions is the syllogism which is the only form of proof whether in demonstrative or deliberative analysis. 8 Hence there are two forms of reasoning, the purely scientific and the inferential. 9 Empiricism as developed in Aristotle was probably due to his associ- ation with medical pursuits, more particularly with the method of Hippocrates who combined remarkable ability of diagnosis with clear insight into the importance of experience. But Aristotle develops and proves his theories not by observation but by reasoning. The observed facts are instances of the general proposition, which when clearly perceived becomes immutable and elevated beyond the possi- ' Met. iv. 5-6. 2 De An. 428, 618. 6 N. Eth. 1098, 63. 3 An. Post. 100, ai6; N. Eth. 1143, a 35- 7 fbid. 1142, azj. 4 De Mem. 451, 632; An. Post. ii. 100, a. 8 Ibid. 1139, a6. 5 Ibid. 91, 633. 9 tirisTi)iioinicbv ical XoyiffTucbv. INTRODUCTION 17 bility of proof or refutation. Concepts were thus clearly stated and then organized. No mere observation, however, had scientific value. The importance of exactly defined investigation was recognized; but only the completely generalized form was an object of knowledge. In the pre-Socratic period matter was the knowable phase of nature. With the Socratic movement form became dominant, and through the categories of possibility and realization Aristotle made an important advance on the Platonic ideas by way of biology. It was in this direction that he developed his psychology. Here he deals not with consciousness but only with the objects of consciousness. For a thing has value for knowledge only if it has the form of a universal. In his scientific treatment, then, Aristotle accepted as given in generalized perception the physical phenomena of which the qualities were to be determined. No attempt was made to analyze the immediate object of knowledge into the conditions out of which it arises, or to investigate the different experiences under these varying conditions. The object of knowledge was presented and then known because of its nature. Therefore it could only be analyzed into more ultimate forms of knowledge, until, when the intuition of final objects of cognition was achieved, the goal of science was also attained. II. DEVELOPMENT OF THE SUBJECTIVE STANDPOINT IN STOICISM i. INTRODUCTION: SOCIAL AND POLITICAL CONDITIONS; CHIEF PHASES OF THE DEVELOPMENT OF THE SUBJECTIVE ATTITUDE It was in the period following the death of Alexander, while the Greek world was in a turmoil of confusion consequent on the splitting up of the empire into separate states, that the post-Aristotelian schools began to formulate their position. The main characteristic of the time from 323 to 280 B.C. was the predominance of the individual, as has been forcibly brought out by recent historians. 1 The desires and advantages of the rulers were of paramount importance; the people were disregarded and were rarely able to assert themselves with success. What the generals of Alexander achieved they owed to their own efforts; for the mingling of the various tribes and nationalities under one government left the leaders without the loyal support accorded a chieftain from his own people and forced them to depend on themselves as individuals. The prominent role that women played in political events is another indication of increasing significance of personal influence. Another significant fact is that the sovereign claimed divine descent or at least a divine mission in order to gain his ends more easily. While among the Greeks who came under the influence of kings the oriental cults and the deification of the rulers transformed the beliefs of the people, in the independent cities, such as Athens, philosophy attempted in various ways to solve the problems raised by these changes in religious convic- tions as well as by Skepticism and also in general by the tendency to make momentary benefits the aim of all endeavor. As philosophy thus attempted both to interpret and to direct this great social movement, the individualistic and subjective point of view gradually superseded the objective standpoint just outlined. It was especially in the search for the criterion of truth that the subjective attitude began to emerge. As a naturalist, Aristotle had viewed the world as a system of specific forms; these complete organisms could be explained by studying the parts in reference to the whole, as means to an end. Thus his investi- gation of soul was a biological treatise in which development, the transi- tion from potentiality to realization, was the keynote. The underlying motive was the desire to exhibit the universal form in the empirical data 1 Cf . Holm Hist, of Greece IV, chaps. 1-3. 18 THE SUBJECTIVE STANDPOINT IN STOICISM 19 of nature and life, since the universal exists potentially in the concrete . Aristotle's problem was determined by his epistemological position (based on the Socratic concept and the Platonic mediation between ideas and particulars) that universals are the only objects of scientific knowl- edge and that the concrete particulars, reality in the strict sense, are presented in sense-perception. Hence no regulating principle was de- manded or furnished; and the search for it became the dominant problem of post-Aristotelian philosophy. Discarding the Aristotelian conception of transcendence, the Stoics developed the other side of the latent dualism, the view of the world as an organism, by adopting the Heraclitean notion of primordial fire, eternal, divine, possessed of thought and will. 1 All existing things partake of this divine substance which appears as hold or bond of union in inorganic matter, as vital principle in plants, irrational soul in animals, and rational soul in man. 2 Together with significant contrasts in ethics the ideal of Aristotle was carried to its logical conclusion; but a new spirit was introduced with the doctrine of universal law and still more by the ever-increasing emphasis on will, self-determination, which involved a practical instead of a theoretical standard of life. The concrete was the object of study; but not the individual in general so much as the particular person. The introduction of assent or acknowl- edgment into the cognitive process by Zeno was the entering wedge of the subjective standpoint. As the volitional attitude gradually became basal in psychology and epistemology, the need of a standard became imperative. It is possible to trace in the older Stoicism the growing emphasis on assent as fundamental in knowledge, the increasing skill in psychological analysis, while the criterion of truth remained dis- tinctly objective. The problems thus raised were bequeathed to the Middle Stoa; then the stress fell on attention and the need of reason in all forms of knowing was recognized. In later Stoicism the judgment, the interpretation, the " view " became of sole importance. The relation between universal and particular, abstract and concrete, remained a vexing problem while the tendency was ever toward a subjective inter- pretation of the universal. Thus when the individual as such asserted himself, the will began to be treated as a specific function, just as Aristotle in contrast to Plato had discriminated activity from the other functions of the soul ; the more analytic point of view tended toward a transforma- tion of the philosophical attitude. 1 Arnim I, 37-44. 3 Pearson Z. 43; Aurel. Med. vi. 14; Sext. ix. 81. 20 SUBJECTIVE VIEWPOINT IN POST-ARISTOTELIAN PERIOD 2. ATTEMPTS AT A THEORY OF KNOWLEDGE ON A SUBJECTIVE BASIS BY THE OLDER STOA A. Doctrine of Assent with Reference to Sense-Perception To the founder of Stoicism ethics was the climax of philosophy; so the study of human nature, individual and social, was basal. More- over, both his physics and his epistemology were psychological in char- acter. His followers also made valuable contributions to psychology in their treatment of assent, motive, and emotion. Of the eight parts or rather functions of the soul enumerated by Zeno, 1 the five senses and reason were cognitive functions. The cognitive soul in its different activities was conceived through analogy of substance and its qualities by Chrysippus; 2 but this logical formulation was undoubtedly founded on Zeno's view of the soul as unified activity. The term ^ye/aovtKoV was used by Zeno 3 and was sometimes identical with tyvxt in the narrower sense; as the controlling soul-function it was active reason. With Zeno's insistence on will, all mental processes became species of judgment 4 and hence the ^y^ovLKov was for him the soul not only as thinking but as willing. The difference between such a definition and Aristotle's tentative characterization of soul is evident; a step had been taken to shift the emphasis from insight to assent. Zeno's particular contribution to the theory of knowledge 5 was, in the first place, the voluntary assent in sense-perception, and in the second, the division of avTao-ia and crvyKara^eo-is, the term ato-Orjcris meant immediate appre- hension. 1 In its wider connotation it comprehended the whole process of sense-perception; the first impression of the object in the sense-organ is unconscious and mechanical and becomes perception in the ^y- POVLKOV to which the stimulation is conveyed; by assent, absolutely certain perception is obtained. Such technical psychological discrimi- nation, which in its precise formulation began with Chrysippus, had a tendency to substitute for the actual experience distinctions made for the sake of exact definition. The Stoics, however, were emphatic in their insistence on the importance of assent, for upon it, they believed, depended knowledge, science, and all forms of activity. This emphasis became more pronounced in the controversy with the Academy. For, in the opinion of the Stoics, moral freedom was involved in this question. Moreover, they made a tacit assumption that assent to an impression implied its correctness. Accordingly, if their opponents acknowledged such assent they also admitted the possibility of certain knowledge. Thus these older Stoics had not only admitted volition as a factor in cognition, but had gradually rendered it basal for all knowledge and hence made a definite approach toward a subjective standpoint. (b) Analysis of the object of knowledge. On the other hand the older Stoa, and Chrysippus in particular against the Skeptics, gave much attention to the characterization of the object of knowledge. For they grounded their doctrine of absolute certainty on the freedom of assent and the objective character of the criterion, using this term in its most usual connotation of that in accordance with which a thing is judged, as a avTa(Tia. KaTaXrjTrTiKr). 2 Since the Stoics used Ka.Taha.fj.(3dveiv in the technical sense, to apprehend, comprehend, a avTao-ta KaToX^im.^ signified an apprehending, knowing impression, one fitted to give knowl- edge and apprehending the object of knowledge. That this was the meaning intended seems clear from the explanation given by Sextus. 3 "The Stoics consider this particular presentation as one apprehending completely the external objects and as absorbing thoroughly the dis- tinctive marks of these objects." 4 Some true fyavraaiai are KaTa\rjTrTiKai, others are not. For they may be true, exact impressions, and yet not be means of certain knowledge. To insure certainty, the impression 1 Plut. De Vir. Mor. c. 3; Plac. vii. 9; Cic. Ac. i. 40. 2 Sext. P.H. ii. 15-16, 22-78; vii. 35, 261. 3 Sext. vii. 248. 4 Cf. ibid. 411 and 247. 26 SUBJECTIVE VIEWPOINT IN POST-ARISTOTELIAN PERIOD must in the first place be from an existing object; and in the second correspond to it, so as to exclude visions of madmen and all forms of illusion; finally it must give accurately all the characteristics of the real object. 1 Hence some peculiar sign is essential, a distinctness which brings conviction of its truth. That the KaraA^-nxou avraa.vra