The 4th century B.C. philosopher, Aristotle, is given credit for the three original laws of logic. In the 17th century A.D. a German logician, Leibniz, formulated a so-called fourth law to close an assumed flaw concluded in the original three (which flaw, if valid, made the laws of logic, themselves, illogical). The ‘Laws of Logic’ (Formal Logic), without which rational discourse cannot be had, are as follows:

1. Law of Non-Contradiction
This law states that two opposing judgments cannot both be true. Both judgments can be false simply because neither one is true. (A) cannot equal (-A).

2. Law of the Excluded Middle
This law states that two opposing judgments cannot be at the same time true and false. One judgment must be true and the other false, for there is no third option (“middle ground”). If one is established as true the opposite judgment cannot also be true. If (A) is (A) then (A) cannot also be (B).

3. Law of Identity
This law states, for example, that each word in a given language must have the same meaning. If there are different meanings to a word (as there usually are in the English language) a proper meaning must be agreed upon in order to have a logical (or intelligible) conversation.

[It is argued whether or not a fourth law is necessary, or if simply qualifying the original definitions to the exclusion of a fourth law is in order.]

4. Law of Sufficient Reason (or Ground)
For example, concerning the original three laws, (A) can be (-A) if they are occurring in different places or at different times. The statement, “It is raining and it is not raining” can be true if the statement concerns two different places and/or at different times. So, (A) “it is raining” and (B) “it is not raining” can both be true in respect to two places and/or times. Without qualifiers {to the first three laws), this law is especially important concerning the third law (Identity) because sufficient reason is paramount when determining which meaning of a word is to be used. However, by simply adding the phrase “…at the same place/time” to the definitions of the laws, the necessity of another law is avoided. For example: (A) cannot, at the same time, equal (-A). Likewise, (A) cannot, at the same time, also be (B). And it cannot possibly be raining at the same place and/or time that it is not raining at that particular place and/or time.

There are other laws, categorized as “second-order laws” (for example, validity, and truth statements; as well as proof formulas, such as syllogisms), which are also a part of formal logic but are beyond the scope of this writing.

It is important to realize that the laws of logic are an expression of the mind of God. Because God has a mind, we, too, have the ability to think. And the laws of logic, whether we admit it or not (it logically doesn’t change the fact), give evidence that God exists.