I have spoken of certitude as being assigned a definite and fixed place among our mental acts;—it follows upon examination and proof, as the bell sounds the hour, when the hands reach it,—so that no act or state of the intellect is certitude, however it may resemble it, which does not observe this appointed law. This proviso greatly diminishes the catalogue of genuine certitudes. Another restriction is this:—the occasions or subject-matters of certitude are under law also. Putting aside the daily exercise of the senses, the principal subjects in secular knowledge, about which we can be certain, are the truths or facts which are its basis. As to this world, we are certain of the elements of knowledge, whether general, scientific, historical, or such as bear on our daily needs and habits, and relate to ourselves, our homes and families, our friends, neighbourhood, country, and civil state. Beyond these elementary points of knowledge, lies a vast subject-matter of opinion, credence, and belief, viz. the field of public affairs, of social and professional life, of business, of duty, of literature, of taste, nay, of the experimental sciences. On subjects such as these the reasonings and conclusions of mankind vary,—“mundum tradidit disputationi eorum;”—and prudent men in consequence seldom speak confidently, unless they are warranted to do so by genius, great experience, or some special qualification. They determine their judgments by what is probable, what is safe, what promises best, what has verisimilitude, what impresses and sways them. They neither can possess, nor need certitude, nor do they look out for it.