There exists what are known as "fallacies" of application of these primary laws. A fallacy is an unsound argument or conclusion. For instance, because a particular man is found to be a liar, it is fallacious to assume that "_all_ men are liars," for lying is a particular quality of the individual man, and not a general quality of the family of men. In the same way because a stork has long legs and a long bill, it does not follow that all birds must have these characteristics simply because the stork is a bird. _It is fallacious to extend an individual quality to a class._ But it is sound judgment to assume that a class quality must be possessed by all individuals in that class. It is a far different proposition which asserts that "_some_ birds are black," from that which asserts that "_all_ birds are black." The same rule, of course, is true regarding negative propositions. Another fallacy is that which assumes that because the affirmative or negative proposition has not been, or cannot be, proved, it follows that the opposite proposition must be true. The true judgment is simply "not proven." Another fallacious judgment is that which is based on attributing absolute quality to that which is but relative or comparative. For instance, the terms "hot" and "cold" are relative and comparative, and simply denote one's relative opinion regarding a fixed and certain degree of temperature. The _certain_ thing is the degree of temperature, say 75 degrees Fahrenheit; of this we may logically claim that it _is_ or _is not_ true at a certain time or place. It either _is_ 75 degrees Fahrenheit or it _is not_. But to one man this may seem _warm_ and to another _cold_; both are right in their judgments, so far as their own relative feelings are concerned. But neither can claim absolutely that it is _warm_ or _cold_. Therefore, it is a fallacy to ascribe absolute quality to a relative one. The _absolute fact_ comes under the Law of Excluded Middle, but a personal opinion is not an absolute fact. There are other fallacies which will be considered in other chapters of this book, under their appropriate heading. CHAPTER XXV. Reasoning. Reasoning, the third great step in thinking, may be said to consist of ascertaining new truths from old ones, new judgments from old ones, unknown facts from known ones; in short, of proceeding logically from the known to the unknown, using the known as the foundation for the unknown which is sought to be known. Gordy gives us the following excellent definition of the term: "Reasoning is the act of going from the known to the unknown through other beliefs; of basing judgment upon judgments; reaching beliefs through beliefs." Reasoning, then, is seen to be a process of building a structure of judgments, one resting upon the other, the topmost point being the final judgment, but the whole constituting an edifice of judgment. This may be seen more clearly when the various forms of reasoning are considered.