A Mini-Lesson in Logical Reasoning

A Mini-Lesson in
Logical Reasoning

“Come now, let us reason together,
says the LORD” (Is 1:18)

“you shall reason with your neighbor” (Lev 19:17)

“[I] lifted my eyes to heaven,
and my reason returned to me” (Dan 4:34)

“Always be ready to give an explanation to anyone who asks you for a reason for your hope, but do it with gentleness and reverence” (1 Pet 3:15)

“What is truth?”
(Jn 18:18)

“The sum of thy word is truth” (Ps 116:160)

“truth came through Jesus Christ” (Jn 1:17)

“I have come into the world,
to bear witness to the truth” (Jn 18:17)

“the truth will make you free” (Jn 8:32)

“I am the way, and the truth, and the life” (Jn 14:6)


Objective Truth
• Truth is objective: “truth is what corresponds to reality”

– Real (Webster’s) = “not artificial, fraudulent, illusory, or apparent”
– Reality (Webster’s) = “the totality of real things and events”
– Truth (Webster’s) = “the body of real things, events, and facts”
– Truth and reality, therefore, are synonymous--the totality of things, events, and facts which are not artificial, fraudulent, illusory, or apparent

• If we share the same reality, then truth for me must be the same as truth for you—truth must be objective

Conflicting theories about truth
• False “subjective” theories of truth

– Pragmatic: “truth is what works”
– Empiricist: “truth is what we can sense”
– Rationalist: “truth is what can be proved by reason”
– Oneness: “truth is the harmony of all ideas”
– Emotional: “truth is what I feel”

• What works, what we see, what is reasonable, the ideas of others, and what we feel, ARE IMPORTANT—but they do not define truth

– Instead, all these important things help us discover the objective truth that was there all along

Human Reason – 3 acts of the mind
• Human reason manifests itself in three acts of the mind:

– Understanding
– Judging
– Reason

• These three acts of the mind are expressed in:

– Terms – either clear or unclear
– Propositions – either true or false
– Arguments – either valid or invalid

• In other words, our mind can understand terms, judge propositions, and reason arguments

Essential Rules of Reason

• A term is clear if it is intelligible and unambiguous
• A proposition is true if it corresponds to reality
• An argument is valid if the conclusion follows necessarily from the premises
• The conclusion must be true if all the terms are clear, the propositions are true, and the argument is valid

Essential Rules of Reason

• To disagree with the conclusion of any argument, it must be shown that either an ambiguous term or false premise or a logical fallacy exits in that argument
• Otherwise, to say “I still disagree” is to say “You have proved your conclusion true, but I am so stubborn and foolish that I will not accept this truth. I insist on living in a false world, not the true one.”

(The above material is an outline for my freshman HS theology session. Much of the above material was adapted from Handbook of Christian Apologetics by Peter Kreeft & Ronald K. Tacelli)

God bless,

Dave