Colquhoun

It may be remarked that there is a very great difference between the assurance of faith, and that assurance of sense which is one of the fruits of faith. The assurance of sense is a believer’s assurance that he is already united to Christ, and is in a state of grace. The assurance of faith is as inseparable from faith as light is from the sun; but it is quite otherwise with the assurance of sense. A man cannot have faith without having an assurance in it, but he may have faith and not have assurance of it. For, though the mind cannot but be conscious of its own act, yet whether that act has the peculiar properties and nature of saving faith cannot be satisfactorily known but by reflection. This assurance of sense or reflection, then, is not a believing in Christ; but it is a believing that we have believed him. It is not a direct act terminating on him, but a reflex by which we are assured of the saving nature of that direct act. But although the direct act may be without the reflect, yet the latter cannot be without the former. A man must begin to believe before he can begin to know that he has believed… The assurance of faith is commonly not so strong nor sweet as the assurance of sense which is supported by evidences. By the former, a man trusts upon the warrant of the free offer and promise that Christ will do the part of a Saviour to him; by the later, he believers upon the inward evidences of grace, that his faith is unfeigned and operative. By the one, he is assured of the truth of what God hath said to him; by the other, of the reality of what God hath wrought in him. By that he trusts he shall be pardoned and saved; by this he is persuaded that he is pardoned and saved in part already. The object of the assurance of faith is Christ revealed, and offered in the Word the object of the assurance of sense is Christ formed and perceived in the heart. The former is the root and the latter is the fruit.

Cited by Donald Beaton “The Marrow of Modern Divinity,” The Princeton Theological Review. 4, no. 3 (1906): 330.

[Note: this distinction arises out of the Westminsterian position on assurance, yet which seeks to integrate the original and classic Augustinian view of faith as entailing assurance. See also Steve Costly’s insightful remark: “When Nicole speaks of assurance, he means assurance of salvation, whereas Calvin spoke of assurance of God’s love.” I should add, that for Calvin, it was an assurance of God’s love through and in the death of Christ, and never apart from it. What is more, what Costly says of Calvin holds good for many other classic and original Calvinists, and what Steve says here captures well the very issues the Marrowmen were trying to express from within the limitations of Westminsterian orthodoxy.]