In his doctrine of the Lord's Supper, John Calvin emphasizes that Christ truly nourishes the souls of believers with his body and blood. This transpires, says Calvin, virtute spiritus sancti--by the power of the Holy Spirit, who is the vinculum--the bond--between Christ and his own. Such pneumatological emphasis does not appear in Calvin's first doctrinal exposition on the sacrament, that is, in his 1536 Institutio, but emerges soon after: first, in 1536 in the midst of the Lausanne Disputation, when he speaks of the Spirit as the bond between believers and the ascended Christ; then, shortly after, in his first catechism for Geneva; and then again, more robustly, with patristic and biblical reference, in the 1539 revision of his Institutio. Given the distinctive emergence of this emphasis in Calvin's thought, the question at the fore of this study is this: What is the provenance--the impetus, the derivation, or source--of Calvin's emphasis on the role of the Holy Spirit with regard to believers' participation in the Lord's Supper, and, further, his particular expression of that emphasis? With due caution regarding the difficulty of discerning the provenance of any particular element of his thought, this study offers a consideration of 1) Calvin's early doctrine of the Trinity, 2) the thought of several of his contemporaries, and 3) his patristic references on this point. In the end, Calvin's emphasis is suggested to be his assimilation of elements deriving from each of these three resources. Finally, Calvin's liturgy is considered, since it exhibits a failure on his part to assimilate his pneumatological emphasis liturgically and euchologically.