Rationality is Morally Necessary

For since the creation of the world His invisible attributes, His eternal power and divine nature, have been clearly seen, being understood through what has been made, so that they are without excuse. For even though they knew God, they did not honor Him as God or give thanks, but they became futile in their speculations, and their foolish heart was darkened. (Romans 1:20, 21 NASB)

Romans 1:20, 21 is the definitive passage that expresses the a priori knowledge of God in man. It seems natural that man, as the image of God (1 Cor. 11:7), would have a priori ideas about God. We probably do not know all the forms or all the information that man has available. But we do know from whom this knowledge comes—Jesus, who is “the true Light which, coming into the world, enlightens every man” (John 1:9 KJV).

There are many interesting theories about what precisely this enlightenment and this a priori knowledge are. Augustine wrote a short little book called De Magistro (roughly translated, Concerning the Teacher) in which he posited a very Platonic idea, which runs thus. Man never learns anything; he only remembers. He gives numerous examples of why he says so and goes round and round with his fifteen-year-old son (the book is written in the form of a dialogue). Augustine’s main argument is that no one can teach any man anything because he must first know the subject on which the teacher would speak before he can understand. If I told you all snarks are delicious, there would be precious little for you to make of this proposition; however, if I told you snarks are delicious, have snouts, cloven hooves, curly tails, a pinkish skin, eat slop, make grunting noises, and taste outstanding when smoked and pan-fried, you would begin to remember the objects that these attributes are commonly associated with and would draw the inference that by snark, I mean pig. And naturally, when we discuss how you knew these attributes of a pig, we would have to inquire into the remembrance of things that occurred when someone first reminded (not taught) you what a pig is. And this would regress to your birth, at which point, Augustine believes his argument is proven that man must be born with a priori knowledge of not only himself and God, but of other objects as well.

This is all very Platonic, and Augustine’s ideas expressed here never really did catch on. Nevertheless, there is a certain value to mentioning it here. If it is true that all men are born with the knowledge of things and need only be reminded of them through interaction with the sensible world then are we also born with the knowledge of good and evil? I believe the answer lies right at the beginning of the Bible.

Then the LORD God called to the man, and said to him, “Where are you?” He said, “I heard the sound of You in the garden, and I was afraid because I was naked; so I hid myself.” And He said, “Who told you that you were naked? . . .” (Genesis 3:9-11 NASB)

The Tree of the Knowledge of Good and Evil has proven to be an exegetical difficulty for many a commentator throughout the ages. I profess it is no easier for me, so I will not undertake to explain the full of its significance here, but will address the consequences of Adam breaking the Lord’s commandment. It becomes clear to us from the account of the Fall that the Tree in some way effected the moral knowledge of good and evil in Adam. We even see that Adam realizes (Augustine: remembers) that he is naked without the explicit revelation of the Lord. That is, God did not tell him he was naked (“Who told you that you were naked?”). From this, we infer that the knowledge of good and evil was something foreign to man in his prelapsarian(1) state. But we did not remain ignorant—Then the LORD God said, “Behold, the man has become like one of Us, knowing good and evil . . .” (Genesis 3:22 NASB). And in some manner, this knowledge of good and evil has resulted in man being wholly set in his heart to do evil alone: “Then the LORD saw that the wickedness of man was great on the earth, and that every intent of the thoughts of his heart was only evil continually” (Genesis 6:5 NASB). It is also by this event that Paul says sin entered into the world and that all men sinned in Adam (Romans 5:12). Even more, the prophet speaking under inspiration of the Holy Spirit said of this condition, “The heart is deceitful above all things, and desperately wicked: who can know it?” (Jeremiah 17:9 KJV).

This brings us to the current topic of why rationality is morally necessary. Man has fallen from his previously perfect state. And note that the use of “perfect” here follows the common biblical meaning of “sinless.” Adam was not perfectly perfect in the sense that God is, but was blameless. Now, however, all men are evil, with wicked and deceitful hearts. It might be inferred from Jeremiah 17:9 that Adam knew his own heart, for it was not deceitful or wicked, but was pure and blameless. As fallen creatures, we do not have this ability, though.

Now, our curse is living with a heart that deceives us. We know the good we ought to do, but our mind provides us with all the excuses we need to not do it. And this should not be missed, of course. What was lost at the fall is the will to do good, not the knowledge or ability to do good. There are many cases in the Bible of postlapsarian man discerning good (Judges 17:13, 1 Samuel 29:9, Job 5:27; 34:4) and discerning what is not good (Ecclesiastes 3:12, Matthew 7:11, Romans 7:18). And this leads us back to vv. 20, 21 in the first chapter of Romans, where we began this entry.

The title of this entry is “Rationality is Morally Necessary.” What I mean to say is that morality is dependent on rationality. Animals, though they have bodies and souls (yes, they do: Genesis 7:15, 22, Ecclesiastes 3:21), they are not the image of God, they are not rational. When God commanded Adam to not eat of the tree, he put it in the form of a proposition: If you eat of the tree then you shall die (Genesis 2:17). Other commands are simply imperatives and not propositions, such as the Ten Commandments. But as objects of knowledge, they are propositions—the eighth commandment forbids stealing; or, if I steal then I am breaking the eighth commandment.

What is morally necessary in the law is the rational basis of the law itself. The law is a standard against which the thoughts and deeds of men are measured. As we have seen, the heart cannot be the standard, for it is deceitful and wicked. Man is not his own judge. This is not to ignore passages such as Romans 14 where it is said that whosoever eats and does not eat of faith, he sins. The heart is not the judge here, but the law, which asserts that whatsoever is not of faith is sin (Romans 14:23) and without faith it is impossible to please God (Hebrews 11:6).

A few weeks ago, we had examined some of the problems with irrationality. Those points apply explicitly to the topic at hand. One point in particular bears repeating.

The obvious problem with irrationality is that it refuses to submit to the Scriptures. Paul says that the Scriptures are sufficient to make a man wise unto perfection. Those who make their own emotions the basis for morality completely ignore the Scriptures’ claim to be the infallible rule of faith.

Irrationality presupposes the non-existence of objective and unequivocal truth. Similarly, though not identically, skepticism, which is the non-cognition of truth, is just as destructive to morality as irrationality. The irrationalist asserts that truth does not exist and the skeptic asserts that truth cannot be known. Both of these assertions necessarily infer that man can neither know good nor evil, and consequently denies the fall and the rational basis of the law. If the proposition, “Stealing is wrong,” is not true, then it follows that man cannot be held accountable for sins. If God’s proposition to Adam in Genesis 2:17 was not true then men should live forever. Even more, we should have no knowledge of good and evil, yet one of the primary arguments for the non-existence of God is the “problem of evil.” The hearts of the heathen do greatly deceive them, for they do not realize (or forget, as Augustine might say) that evil exists as the contradictory of good, and that only objective, universal truth can provide the necessary basis for moral good and evil.

Soli Deo Gloria


(1) Prelapsarian means “before the fall.” Postlapsarian would be “after the fall.”