Is Some Knowledge A Priori?

The following is adapted from a post at Tough Questions Answered:

Philosophers who study how we know things (epistemologists) have long debated whether we have innate or intuitive knowledge. This kind of knowledge is often referred to as a priori knowledge. It is knowledge that one has prior to, or independently of, sense experience. It cannot be proven by experience.

The debate over a priori knowledge is important to theists because naturalists often deny the existence of most kinds of a priori knowledge and claim that we can only know what we observe with our senses. That is, they tend to be empiricists and hold that all significant knowledge is known a posteriori.

However, do we know that raping little children for fun is wrong? Most people would say “yes”, but this is an example of a priori knowledge, because we don’t come to this conclusion by observing the world around us – we just know intuitively that raping little children for fun is wrong.

Consider the following eleven examples of propositions that have been proposed as a priori knowledge by epistemologists. They're taken from several different categories of knowledge: mathematics, knowledge of “greater than,” laws of logic, morality, deductive logic, causality, knowledge of space, knowledge of God, and introspective knowledge:

1. If John is taller than Mary and Tom is taller than John, Tom is taller than Mary.
2. 5 + 7 = 12
3. Nothing is both red and green.
4. Some sentences are not both true and false.
5. If Socrates is a man and all men are mortal, Socrates is mortal.
6. Every event has a cause.
7. All material objects have size.
8. A greatest possible being necessarily exists.*
9. It is wrong to harm people just for the fun of it.
10. If I believe I exist, I exist.
11. P and not-P cannot be both true at the same time in the same way.

In order to be an example of a priori knowledge the proposition has to be true and not believed on the basis of perception, memory, or testimony. It must be self-evident and we must apprehend it intuitively.

So, do you believe that any of the above examples are known apart from any sense experience other than that involved in learning the meaning of the words? If so, you believe there is some knowledge that we have a priori. * This is the conclusion of what's called the ontological argument for the existence of God.