The basic laws of right thinking have been known since the time of Aristotle. And regardless of how old you and your interlocutor are, what are your occupations, social statuses and even what you think about logic in general, these laws continue to operate and they can not be replaced or deleted.
We apply the laws of logical thinking daily. And even unconsciously always notice if at some point they are violated. From the point of view of psychology, non-observance of the basic laws is a disorder of thinking .
The law of identity
This law says that any concept is identical to itself. Each statement must have an unambiguous meaning, understandable to the interlocutor. Words should be used only in their true, objective meaning. Substitution of concepts, puns also refer to the violation of the basic laws of logical thinking. When one subject of discussion is replaced by another, each side makes a different sense, but the conversation is perceived as a discussion of the same thing. Often, substitution is deliberate and has the goal of misleading a person for the sake of some benefit.
In Russian there are many words that are the same in sounding and even spelling, but different in meaning (homonyms), so the meaning of such words is revealed from the context. For example: "Fur coats from natural mink" (we are talking about fur) and "Dug a mink" (from the context it is clear that in this phrase is meant a burrow for animals).
Substitution of the meaning of the concept leads to violation of the law of identity, because of which there is misunderstanding on the part of the interlocutors, conflicts or erroneous conclusions.
Often the law of identity is violated because of a vague idea of the meaning of the discussion. Sometimes one word in the representation of individual people has a completely different meaning. For example, "erudite" and "educated" are often considered synonymous and not used in their own meaning.
The law of non-contradiction
Proceeding from this law, it follows that with the truth of one of the opposing thoughts, the rest will necessarily be false, regardless of their number. But if one of the thoughts is false, this does not mean that the opposite will necessarily be true. For example: "Nobody thinks so" and "Everybody thinks so". In this case, the falsity of the first thought does not yet prove the truth of the second. The law of non-contradiction is valid only if the law of identity is observed, when the meaning of the discussion is unambiguous.
There are also compatible thoughts that do not deny each other. "They are gone" and "they came" can be used in one sentence with a reservation for a time or place. For example: "They left the cinema and came home." But at the same time it is impossible to leave and come to one place. We can not simultaneously assert a phenomenon and deny it.
The law of the excluded third
If one statement is false, then the contradictory statement will be true. Example: "I have children," or "I have no children." The third option is impossible. Children can not be theoretically or relatively. This law implies the choice of "or-or". Both contradictory statements can not be false, nor can they be true at the same time. Unlike the previous law of correct thinking, here we are talking not about opposing, but about conflicting thoughts.
Law of good reason
The fourth law of right thinking was discovered later than the previous. It follows that any thought should be justified. If the statement is not fully substantiated and not proved, then it may well not be taken into account, because will be considered false. Exceptions are axioms and laws, because they have already been confirmed by many years of experience of humanity and are considered a truth that no longer needs any proof.
No statement, no reason or thought can be considered true unless they have sufficient evidence.