“Logic is the process of proper inference. It is the system of thinking properly–of arriving at proper conclusions. It is the process of proper thinking based upon principles that govern the validity of arguments.” What is logic? CARM

Law of thought: any of the three basic laws of traditional logic: the law of contradiction, the law of excluded middle, and the law of identity.” Dictionary.com

“These three laws are thought to have originated with Aristotle, who believed that the laws are necessary conditions for rational thinking to occur. The three laws are the law of identity, law of non-contradiction, and law of the excluded middle.” The Three Laws of Logic, Study.com

Keeping the following three laws in mind will be of great help in your apologetics work or during any evaluation or formulation of reason.

The Law of Excluded Middle: Statements are either false or true. There is nothing in between or other option. The statement “The lamp is on” is either false or true. The lamp cannot be sort of on. (No dimmers here)

The Law of Identity: A is A. Things are what they are. A statement that is true is true. If the statement “The lamp is on” is true, then it is true.

The Law of Non-contradiction: A statement cannot be false and true in the same way.  If the statement “The lamp is on” is true then it cannot also be false at the same time. The lamp must not be off.

Sound reasoning is indispensable in the life of the believer and by extension in the work of apologetics. God gave us a mind that can reason logically for a good purpose. We can use logical thoughts to defend Him and His word. There are a lot of beliefs and teachings that differ from Christianity. When we speak about these things with others, contradictions come up. Gently pointing out contradictions in a loving way, offering any relevant biblical testimony, and stating that two opposing ideas cannot both be true, sometimes helps to bring people to a place where they can begin to see that something is amiss. This is an important work in apologetics.

In and of itself, logic is important; but it does not save. That belongs to God. But with the His help, we can try to shed light on faulty reasoning and erroneous beliefs to His glory. We can pray that by His grace and the work of the Holy Spirit, the unbelieving come out of darkness.

See Also
List of Logical Fallacies with Examples
How to Spot Logical Fallacies