"Ye shall know the truth, and the truth shall make you free." What is this truth, from what are we to be freed, and what is it to know the truth? In thinking upon these questions it is clear that a thing must be, before it can be known. It must have reality, being, existence, in order that there may be somewhat to be known. We cannot know that which is not; but we may believe that to be which is not, and may entertain all manner of beliefs and opinions about that which in reality has no existence whatever. To know a thing, therefore, as distinguished from a mere opinion or belief about it, means to know it in its true nature, being, or reality. There is all the difference imaginable between knowing a thing and believing a thing. We may believe a thing, give our mental assent to it with more or less confidence, and yet the thing may continue to lie, as it were, on the outside of our consciousness indefinitely; but when we truly know a thing, we completely assimilate the thing, take it into our consciousness in such a manner that it becomes a part of us, constitutes a part of our very being or life. Thus, we may have been figuring on a life-basis of two times two are five, until after a while, we become convinced that two times two are four; then we can no longer believe that two times two are five, for two times two are four has become a part of our conscious being, and since it is the truth, it is permanent and abiding and can never be destroyed, but must forever continue to be a part of our consciousness.
The well-known definition of reality given by one of our modern philosophers; namely, "persistency in consciousness," is exceedingly interesting in its far-reaching suggestiveness. The belief that two times two are five is temporal; for, being error, it was always liable to be destroyed—cast out—either here or hereafter, by the truth that two times two are four. We could never know that two times two are five we could believe it and have all manner of opinions about it, and some of our opinions might appear to us to be very real, but we can know only that which truly is; viz., two times two are four. It thus begins to appear that "truth" and "reality" are in fact convertible terms; in their last analysis they merge into each other and become really but two words for one and the same thing. Whatever is real is true, and whatever is true is real, permanent, and abiding.
This distinction between knowing and believing, between truth and error, between that which is real, permanent, and abiding, and that which is unreal and temporal, has been familiar to philosophy since more than five hundred years before Christ, and presents some of the most fundamental and familiar problems with which reflective thought has concerned itself in all ages. It found its earliest definite statement in the Eleatic school of Greek philosophy, of which Parmenides b.c. 536) was perhaps the best representative; "He was the first to distinguish carefully between truth [aletheia] and opinion [doxa] between ideas obtained through the reason and the simple perceptions which are based on sense. Assuming that reason and sense are the only sources of knowledge, he held that they furnish the mind with two distinct classes of cognitions,—one variable, sary, and uncertain [doxa]; the other immutable, necessary, and eternal [altheia].... Whatever, therefore, manifests itself in the field of sense is merely illusory—the mental representation of a phenomenal world," etc.
