We have shown that a belief in the reality of the existence, both of mind and of matter, as _causes_, is one of the implanted principles of mind. Some philosophers have claimed that there is nothing in existence but mind, and that all that is called matter is simply _ideas_ of things in the mind itself, for which there is no corresponding reality. Others have claimed just the opposite: that there is no such existence as an immaterial spirit, but that soul is the brain, or some other very fine organization of matter. In both cases, the assumptions not only have no evidence to sustain them, but are contrary to the common sense or reason of all mankind, and never can be really believed. When _perceptions_ are called into existence by the agency of the senses, we can not help believing that things _are as they appear to us_, unless we have some evidence of deception either from disordered sensation or some other cause. But in regard to our _conceptions_ we have two classes. One class is attended with the belief that they correspond with realities, or the things they represent. The other class is not attended with this belief. For example, we can conceive of a house of a color, form, and details such as we never saw, and this conception is not attended with any belief of the reality of such an existence; but when we conceive of the home of our childhood, this conception is attended with a belief of the reality of the thing conceived. This illustration furnishes the means of defining "_truth_" as "_the reality of things_." We _conceive_ the truth when our conceptions represent correctly the reality of things, and we _believe_ the truth when we feel this correspondence to exist. We believe falsehood when we have a conception attended by a feeling that it represents the reality of things when it does not. All our comfort, success, and happiness depend upon _believing the truth_; for just so far as our belief or faith varies from the reality of things, we shall meet with mistakes, disappointment, and sorrow. Our beneficent Creator has so formed our minds and our bodies that, in their natural, healthy state, our _perceptions_ correspond with the reality of things uniformly, while, as before stated, our belief or faith also thus corresponds. It is very rarely the case that disease or other causes prevent this uniform correct perception and belief in regard to all things that come within the reach of our own senses. It is only in regard to that knowledge that we gain from the _experience and testimony_ of others, or from the _process of reasoning_, that we become liable to a false belief. Men often impart their conceptions of things to us, and we find that they do not correspond with realities. We also, by a process of reasoning, often come to conceptions of things, and a belief in them, which we find to be false. _Evidence_ may be defined as all those causes which tend to produce _correct_ ideas of truth or the reality of things.