When, then, philosophers lay down principles, on which it follows that our assent, except when given to objects of intuition or demonstration, is conditional, that the assent given to propositions by well-ordered minds necessarily varies with the proof producible for them, and that it does not and cannot remain one and the same while the proof is strengthened or weakened,—are they not to be considered as confusing together two things very distinct from each other, a mental act or state and a scientific rule, an interior assent and a set of logical formulas? When they speak of degrees of assent, surely they have no intention at all of defining the position of the mind itself relative to the adoption of a given conclusion, but they mean to determine the relation of that conclusion towards its premisses. They are contemplating how representative symbols work, not how the intellect is affected towards the thing which those symbols represent. In real truth they as little mean to assert the principle of measuring our assents by our logic, as they would fancy they could record the refreshment which we receive from the open air by the readings of the graduated scale of a thermometer. There is a connexion doubtless between a logical conclusion and an assent, as there is between the variation of the mercury and our sensations; but the mercury is not the cause of life and health, nor is verbal argumentation the principle of inward belief. If we feel hot or chilly, no one will convince us to the contrary by insisting that the glass is at 60°. It is the mind that reasons and assents, not a diagram on paper. I may have difficulty in the management of a proof, while I remain unshaken in my adherence to the conclusion. Supposing a boy cannot make his answer to some arithmetical or algebraical question tally with the book, need he at once distrust the book? Does his trust in it fall down a certain number of degrees, according to the force of his difficulty? On the contrary, he keeps to the principle, implicit but present to his mind, with which he took up the book, that the book is more likely to be right than he is; and this mere preponderance of probability is sufficient to make him faithful to his belief in its correctness, till its incorrectness is actually proved.