This dissertation addresses teleology in the writings of Aristotle and in relation to modern mechanics. In chapters one through three, I argue that Aristotle's teleology is theoretically grounded in the claim that both as an explanatory and as a causal factor, actuality is prior to potentiality. As actualities, therefore, both form and function are prior to the material and efficient causes that condition their occurrence in nature. In chapters four and five, I then consider the recent 'systems' or 'cybernetic' view of goal-directedness, along with some basic features of mechanical systems and laws more generally, in light of Aristotle's teleology. I conclude that from an Aristotelian point of view there is no conflict between teleological and mechanical approaches to nature.