The Principle of Fulfillability

By Sarah R. Enterline

Currently, the most well-known syllogism on the argument from desire for God’s existence is the one officially formulated by Dr. Peter Kreeft. Below I examine it, critique it, and propose that it be adjusted before it continues to be used as an argument for God’s existence moving forward:

Premise one of Kreeft’s syllogism states that “Every natural, innate desire in us corresponds to some real object that can satisfy that desire.”[1] Notice it says that every desire corresponds to some real object that can satisfy it. Meaning that what we desire probably exists otherwise we wouldn’t know to desire it in the first place. C.S. Lewis wrote, “Creatures are not born with desires unless satisfaction for these desires exists. A baby feels hunger; well, there is such a thing as food. A duckling wants to swim; well, there is such a thing as water… If I find in myself a desire, which no experience in this world can satisfy, the most probable explanation is that I was made for another world. If none of my early pleasures satisfy it that does not prove that the universe is a fraud. Probably earthly desires were never meant to satisfy it, but only to arouse it, to suggest the real thing.”[2] Dr. Geisler refers to this as the argument from need: if humans really need something, its fulfillment probably exists, and the fulfillment could be other-worldly.

To me, this proves God exists, simply because religion exists. There had to be some real object that man desired a relationship with or wanted to worship, otherwise, religion would have never come to be. As a high school teacher, I let my students debate this topic. I love discussing theories with young people, because one, they are extremely smart, and two, usually they are free of enough pre-conceived notions to innocently ask the next logical question. So one of my students challenged me and said, “Well I desire a unicorn, but that doesn’t necessarily mean it exists.” That took me a few minutes to respond to because to be able to desire something imaginary meant that even though we desire that He exists, God could possibly be made up as well. (Also related to Freud’s “wish fulfillment” or what is known as “fantasy desires”).

However, the answer finally came to me. You see, my student would have never thought to desire a unicorn unless she had some a priori reason to do so, meaning she had heard about a unicorn sometime in the past. Information does not come from non-information. If she had never heard of a unicorn before, she would have never known to desire it. Our desires can be fulfilled because we desire them a posteriori, or after the information about such a thing is given to us. This is what I call the Principle of Fulfillability: that humans cannot desire something unless its fulfillment exists, otherwise they would have never known to desire it in the first place.

That begs the question of how the first person that invented the idea of the creature known as the unicorn came by their thought. There are two possibilities. First, there was actually a creature called a unicorn but it somehow went extinct and so now all we have left is the memory of it (possible, but unlikely). Or second, the person had known of two things that do exist in reality, namely horses and horns, and decided to put them together to create a new fantasy creature. That would not be a case of non-information giving rise to information, but simply some clever person combining two pieces of existing information to create a new hybrid of information, a fantasy, if you will. This is not some rare event, as mankind does this all the time; it is called “inventing” or “imagining”. The fact that the idea of the unicorn exists does not mean that anything we could ever imagine must exist in reality. Some things only exist as ideas, and therefore, do not require a real fulfillment. (Also, Kreeft qualified that only natural, innate desires correspond to real objects. A unicorn is not a natural desire. It is an “imagined” one, and therefore does not need to correspond to a real object.).

This, of course, begs another question: could God be one of those “fantasy” or “imagined” desires?

Geisler writes, “For now, it will suffice to say that the mere universality of religious experience is by no means a guarantee of its reality or a sure indication of its unreality. Human experiences reveal that some desires are fulfillable and some are not. Which class religion falls into will have to be determined by some criteria other than the experience itself.”[3] This means that there could be desires of humans that remain unfulfilled, simply because they are imagined hybrids of learned information that simply don’t exist in reality. Now, we need to ask which type of desire God is – an imaginary hybrid of a posteriori information or the result of an a priori information-Giver?

Notice as well that the first part of premise one of Kreeft’s syllogism states that, “Every natural, innate desire in us corresponds to some real object that can satisfy that desire.” Kreeft here is asserting that mankind is born with natural, innate desires. A primary information-Giver would certainly explain that, as well as why mankind has the various specific and unique desires that he does. Kreeft elaborates: “The first premise (of the syllogism) implies a distinction of desires into two kinds: innate (natural) and externally conditioned (artificial). We naturally desire things like food, drink, sleep, (or things necessary for life) but also knowledge, friendship and beauty.”[4]  Kreeft is asserting here that we naturally desire things that are more than just those that are necessary for continuing our physical existence, and that they aren’t learned or socially conditioned, but have always been there.

Kreeft continues in his premise two and conclusion: “But there exists in us a desire which nothing in time, nothing on earth, no creature can satisfy. Therefore there must exist something more than time, earth and creatures, which can satisfy this desire.”

If we do desire something more – why, and what is it? Are we talking about Plato’s forms here? This is where I feel Kreeft’s argument is too vague. It acts more as an argument for general, metaphysical desires, and less as a specific argument from desire for God’s existence.

I do agree with Kreeft that we desire metaphysical things, but those don’t necessarily mean God exists, though His existence makes those things more possible and probable. If we desire God Himself, then the syllogism becomes an argument from desire for God.

Therefore, I propose the following should be used instead:

1: Human beings desire a relationship with the Divine. (Evidence: The Imago Dei – read here, and Religion exists – read here.)

2: Humans cannot desire something unless its fulfillment exists. (The Principle of Fulfillability – above)


3. A Divine being capable of relationship with human beings must exist.


[1] Kreeft, Peter, and Tacelli, Ronald K. Handbook of Christian Apologetics. Downers Grove, IL: InterVarsity Press, 1994; p. 78.

[2] Lewis, C.S. Mere Christianity. New York, NY: Macmillan, 1960; p. 120.

[3] Geisler, Norman L. Philosophy of Religion. Grand Rapids, MI: Zondervan, 1981; p. 25

[4] Kreeft, Peter, and Tacelli, Ronald K. Handbook of Christian Apologetics. Downers Grove, IL: InterVarsity Press, 1994; p. 78.

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