In Laws II.vii.5:
The truth is, that the mind of man desireth evermore to know the truth according to the most infallible certainty which the nature of things can yield. The greatest assurance generally with all men is that which we have by plain aspect and intuitive beholding. Where we cannot attain unto this, there what appeareth to be true by strong and invincible demonstration, such as wherein it is not by any way possible to be deceived, thereunto the mind doth necessarily assent, neither is it in the choice thereof to do otherwise. And in case these both do fail, then which way greatest probability leadeth, thither the mind doth evermore incline. Scripture with Christian men being received as the Word of God; that for which we have probable, yea, that which we have necessary reason for, yea, that which we see with our eyes, is not thought so sure as that which the Scripture of God teacheth; because we hold that his speech revealeth there what himself seeth, and therefore the strongest proof of all, and the most necessarily assented unto by us (which do thus receive the Scripture) is the Scripture. Now it is not required or can be exacted at our hands, that we should yield unto any thing other assent, than such as doth answer the evidence which is to be had of that we assent unto. … [I]n all things then are our consciences best resolved, and in most agreeable sort unto God and nature settled, when they are so far persuaded as those grounds of persuasion which are to be had will bear.
Which thing I do so much the rather set down, for that I see how a number of souls are for want of right information in this point oftentimes grievously vexed. When bare and unbuilded conclusions are put into their minds, they finding not themselves to have thereof any great certainty, imagine that this proceedeth only from lack of faith, and that the Spirit of God doth not work in them as it doth in true believers; by this means their hearts are much troubled, they fall into anguish and perplexity: whereas the truth is, that how bold and confident soever we may be in words, when it cometh to the point of trial, such as the evidence is which the truth hath either in itself or through proof, such is the heart’s assent thereunto; neither can it be stronger, being grounded as it should be.