Laws of Reasoning

The Principle of Sufficient Reason

The principle of sufficient reason states that everything (whether it is a thing, an event, or a proposition) must have a reason or a cause. This is presupposed in reasoning about anything because, after all, when reasoning about something, we are presupposing that it happens (or exists or is true) for a reason. There are several different versions of the principle of sufficient reason. Here are three:

1. For every entity X, if X exists, then there is a sufficient explanation for why X exists.
2. For every event E, if E occurs, then there is a sufficient explanation for why E occurs.
3. For every proposition P, if P is true, then there is a sufficient explanation for why P is true.

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Law of identity

\ The law of identity states that a is a, (For example a dog is a dog, a dog is not a cat.”

\ The identity of a thing has to do with the actual properties that a thing possesses and, without which, it would not be the thing in question. Whatever a thing is, it is what it is and does not have alternative or multiple identities. (If it did, they would be part of its identity.)

Fundamental to our thinking, then, is the view that something cannot be both what it is and, at the same time and in the same respect, other than what it is. If a thing did not have an identity and was not identical to itself, then it would be unintelligible.

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Law of non-contradiction

\ The law of non-contradiction states that a proposition cannot be true and false at the same time.

\ Example: So, for example, if you believe that "Today is Wednesday" and Today is not Wednesday" at the same time (Eastern Standard) and in the same respect (not "Today is Wednesday, but it sure feels like Tuesday"), then you hold a contradiction.

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Law of the excluded middle

The law of the excluded middle states that a specific proposition is either true or false. There is no middle ground, such as sort of true or neither true nor false.

\ Example: The proposition may be true on July 23, 2010, In Toronto, Ontario, but false at the same time in North Bay, Ontario. The proposition could be false in the same place in Toronto but on different data, such as July 24, 2010.

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Ockham’s Razor

The simplest explanation or theory is the best choice. The simplest explanation is the one that makes the fewest assumptions and uses the fewest entities to explain the same facts.