Assurance of salvation is a matter of perennial pastoral concern and theological controversy. After the Great Awakening, Jonathan Edwards developed a doctrine of assurance based largely on discerning the work of the Spirit in the affections and actions of the professed believer. One might have expected from this theocentric, trinitarian and surprisingly participational theologian a robust doctrine of assurance and a joyful, other-centred spirituality. Ironically, however, profound ambiguities persisted within it which will be shown to arise from the predominantly pneumatic nature of his version of theosis, a blurring of the distinction between justification and sanctification, and the power of his predominantly psychological analogy of the Trinity. This article will therefore first present the main features of Jonathan Edwards’ doctrine of the assurance of salvation. The second section will evaluate it by outlining factors in Edwards’ theology which might have been expected to produce a high level of certainty concerning assurance, and then those which might militate against this certainty. Whilst Edwards did at times espouse the social analogy of the Trinity, his theosis is constructed predominantly within the psychological analogy. Innovatively modified though it was, because Edwards works within this framework, he overemphasises the pneumatological union of the saints with God, at the expense of the incarnational union of God with and for humanity in Christ. This results correspondingly in an inordinate reliance for assurance on the Spirit's work within the realm of human subjectivity, over against objective christological realities. In short, Edwards’ theology of assurance is, in the end, individualistic and anthropocentric.