3. What _truth_ is, hath been defined in the precedent chapter; what _evidence_ is, I _now_ set down: and it is the concomitance of a man’s _conception_ with the _words_ that signify such conception in the act of ratiocination: for when a man reasoneth with his lips only, to which the mind suggesteth only the beginning, and followeth not the words of his mouth with the conceptions of his mind, out of custom of so speaking; though he begin his ratiocination with true propositions, and proceed with certain syllogisms, and thereby make always true conclusions; yet are not his conclusions _evident_ to him, for want of the _concomitance of conception_ with his words: for if the words alone were sufficient, a _parrot_ might be taught as well to know truth, as to speak it. Evidence is to truth, as the sap to the tree, which, so far as it creepeth along with the body and branches, keepeth them alive; where it forsaketh them, they die: for this evidence, which is meaning with our words, is the life of truth. [Sidenote: Science defined.] 4. Knowledge thereof, which we call _science_, I define to be _evidence of truth_, from some beginning or principle of _sense_: for the truth of a proposition is never evident, until we conceive the meaning of the words or terms whereof it consisteth, which are always conceptions of the mind: nor can we remember those conceptions, without the thing that produced the same by our senses. The _first_ principle of knowledge is, that we have such and such _conceptions_; the _second_, that we have thus and thus _named_ the things whereof they are conceptions; the _third_ is, that we have _joined_ those _names_ in such manner as to make true propositions; the _fourth_ and last is, that we have _joined_ those _propositions_ in such manner as they be concluding, and the truth of the conclusion said to be known. And of these two kinds of knowledge, whereof the former is _experience of fact_, and the latter _evidence of truth_; as the _former_, if it be great, is called _prudence_; so the _latter_, if it be much, hath usually been called, both by ancient and modern writers, _sapience_ or wisdom: and of this _latter_, _man_ only is capable; of the _former_, _brute beasts_ also participate. [Sidenote: Supposition defined.] 5. A proposition is said to be _supposed_, when, being _not evident_, it is nevertheless _admitted for a time_, to the end, that, joining to it other propositions, we may _conclude_ something; and to _proceed_ from conclusion to conclusion, for a _trial_ whether the same will lead us into any _absurd_ or impossible conclusion; which if it _do_, then we know such supposition to have been false. [Sidenote: Opinion defined.]