Five Reasons to Make Logic a Part of Your Life

written by Dr. Doug Potter

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A long time ago in our galaxy, Southern Evangelical Seminary (SES) started a blog series on informal fallacies. Years before I ever took a class on logic, an atheist on my college campus once told me that if I read a logic text, I would see the problems with Christianity and leave the faith. Over the years, I have run into believers who also think the Christian faith contains contradictory teaching but believe it anyway. Some believers not only shy away from logic, but they think such a study is detrimental to personal faith.

Dr. Peter Kreeft in his excellent text on logic reminds us, “No course is more practical than logic, for no matter what you are thinking about, you are thinking, and logic orders and clarifies your thinking . . . [logic studies] the basic forms (structures) and the basic laws (rules) of thought. . . .”¹

One goal of the SES blog series is to motivate readers to study logic by showing that such a study is not a threat to Christianity or one’s faith. Instead, logic is a powerful tool to use in the demonstration of truth and the destruction of speculation raised up against the knowledge of God (1 Corinthians 10:5). Regardless, if you have read all the blogs, I would like to conclude the series by reiterating five important things about logic, five reasons to make logic a lasting part of your life.

1. God Is the Basis of Logic

One of the first questions answered in a good logic class is how is logic related to God? Because we are the creature and God is the Creator, we must answer the question in terms of God’s nature and our knowing. Since God is identical to His nature or being, God alone is a simple, uncreated infinite Being. Hence, ontologically speaking, God is Logic and the basis of all logical thinking by creatures. Humans did not invent logic. They can only discover it. God is the author of all rational thought. Logic, therefore, must flow from His infinite nature.

While God can do what is humanly impossible (Luke 1:37), He cannot do what is actually impossible (Hebrews 6:18). God cannot be logically contradictory (illogical) any more than He can change His nature or stop existing.

2. There Are Two Views of Logics

By saying two logics, I do not mean a western and eastern logic as some claim. No, in this sense there is only one logic because all humans have the same kind of rational nature. It just so happens Aristotle wrote the first book (we know about) on logic about 400 years before Christ.

The two logics I have in mind are explained by Dr. Kreeft.² From Aristotle until the eighteenth century, everyone studied one and the same logic. Such study flowed out of philosophical realism. It said, as Kreeft puts it, “The object of human reason, when reason is working naturally and rightly, is objective reality as it really is; that human reason can know objective reality and can sometimes know it with certainty.”³ The alternative view, the second logic, came in the eighteenth century flowing out of the philosophy of Locke, Hume, and Kant. They came to believe, as Kreeft says, “that the immediate object of human knowledge is our own ideas rather than objective reality.”⁴ A world of difference indeed!

This second approach produced a mathematical or symbolic approach to logic. This was fully realized in the impressive volume Principia Mathematica (1913) by Bertrand Russell and Alfred North Whitehead. Logic even today, especially in academia, has been centered more on this symbolic approach.

Now don’t get me wrong. There are important things to be said about the second logic sometimes called symbolic logic. Almost all philosophy majors take and should take (despite their cries of outrage) a class in symbolic logic. What is worse still, today many philosophers criticize the first logic, Aristotle’s logic, as being assuming or naïve. That is why we must never forget #3.

3. Logic Applies to Reality

That logic applies to reality is an undeniable truth. If you try to deny it, you will be affirming it. If someone says “logic does not apply to reality,” it is self-defeating since it is relying on the very kind of application or correspondence it is denying. Human beings or persons, not just my thinking mind, really do exist. It is not just propositions and terms in my mind that exist. But things such as bricks, animals such as bears, and people who are really bachelors do exist and have natures that can be known by us.

It is because logic applies to reality that we can make arguments and reason in a valid or invalid manner and that we can distinguish a sound argument from a fallacious one. It is because logic applies to reality that we can soundly argue for the existence of God and reason about the evidence for Christianity and that we can discover and demonstrate truth in every human discipline, including Christian apologetics, theology, and ethics.

4. The Bible and Jesus Use Logic

The Bible not only assumes logic, but it also uses logic. From Genesis to Revelation, the Bible employs the laws of logic. Whenever the Bible affirms God, it is using the law of noncontradiction by denying its opposite, that there is no God (Genesis 1:1). Whenever the Bible affirms God is who He is, it is using the law of identity (Exodus 3:14). Whenever the Bible affirms something about God and denies something about God, it uses the law of excluded middle (Numbers 23:19). Any thought or statement about God, including ours, cannot escape the laws of logic.

Jesus of Nazareth, like the Bible, used the laws of logic, as witnessed by His use of logical arguments. He used reasoning that involved A fortiori (Matthew 12:9-14), Disjunctive Syllogisms (Matthew 12:30 linked with Luke 11:23), Hypothetical Syllogisms (Matthew 22:41-46), and Categorical Syllogisms (Luke 6:6-11). Additionally, he avoided the Horns of a Dilemma (Matthew 22:15-22) and used Reductio Ad Absurdum (Matthew 22:22-28).⁵

The apostles following their Master’s lead used logic and arguments in reasoning with unbelieving Jews and Gentiles (see Acts 9:29 17; 18; 19) to show that Christianity is true. And yes, they not only used it to help win converts and establish churches, but they even used it in churches. When Paul wrote the longest letter in the New Testament, he filled it with logical arguments.⁶ It was then read in Rome to a young church, a church Paul feared he would never be able to visit and to teach in person.

Indeed, it is worth pointing out that every time a biblical prophet states a valid and sound argument, he is avoiding all the formal and informal fallacies. Also, no Christian doctrine such as the Trinity, the incarnation of Christ, or God’s sovereignty and human free will is contradictory. They may involve mysteries or not be fully comprehended by a finite mind, but they do not and cannot suffer contradiction.

5. Not Everything Needs a Logical Justification

As important as the study of logic is, proofs and arguments have limitations. For example, the fact that our intellect knows things in the world is simply evident to us. It does not need a proof to be justified. As my logic professor Dr. Richard Howe says, “If the brick wall does not convince you that it exists, what makes anyone think an argument about the brick wall will do any better.” Likewise, first principles, such as the whole is greater than the parts, do not need, nor can they have a logical defense. Yet, their truth is exhaustively known, once understood.

Most important, people do not need an argument or a proof to believe in the Gospel of Jesus Christ. There is an important distinction to make between believing that something is true and believing in something. Using formal logic or finding informal fallacies cannot save anyone. Yes, it might save someone from the pain of contradiction, but it cannot save your soul. To believe in Jesus Christ one must just hear the Good News (Romans 10:14-15).

Unbelievers may need a logical apologist to remove obstacles that impede them from believing in the Gospel (1 Corinthians 15:3-8) and from having everlasting life (John 3:16). Reason and evidence are needed to show that God exists or that the claims of Christ are true. Believing that it is true involves the intellect. Believing in involves the will, and the intellect only supports the will to believe in the Gospel— a subtle but important distinction. Thus, we are obligated to give an answer (1 Peter 3:15), but no human argument can cause someone to belief in Christ. Only the work of God through the Holy Spirit can save.


Logic 101 Here I Come

Everyone, especially Christians, should embrace the study of logic. It should be a prerequisite for those doing apologetic based ministry and perhaps any ministry. So, we invite you to take a class on logic at Southern Evangelical Seminary. You can take it just for personal enrichment or academic credit. SES offers logic for all levels, from basic to advanced, online and on campus. Make it a part of your life as you minister to others in your area of influence.

Logic is a gift from God that can help rational creatures manifest the goodness of God in this world and invites us to experience the illumination of God in the world to come (Revelation 22:5).

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  1. Peter Kreeft, Socratic Logic: A Logic Text Using Socratic Method, Platonic Questions, and Aristotelian Principles, 3.1 ed. (St. Augustine’s Press, 2010), 1.
  2. Ibid., 15-25.
  3. Ibid., 17.
  4. Ibid., 18.
  5. See Norman L. Geisler and Patrick Zukeran, The Apologetics of Jesus (Baker Books, 2009), chap. 4.
  6. See Shawn Nelson, Romans in Logical Form (Bastion Books, 2014).






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