From answering the above questions you should now have some idea of the Rationalist approach to knowledge. Perhaps it would help at this point to look at the concept of necessity in a little more detail.

Necessity is commonly split up into three types:

1) Logical. When something is logically necessary it is true by definition. For example, the statement "All bachelors are unmarried" is necessarily true because that is how we define the word "bachelors" - that is, "people who are unmarried". Mathematical truths are also of this type. These are called necessary or analytic truths.

2) Empirical. Something is empirically necessary when it could have happened otherwise but didn't. So, it might be an empirical necessity that there are no orange elephants or that I have to go to sleep at some time. Someone might talk of it being "unthinkable" not to act in a certain way, as if it were impossible not to, or for it to be "impossible" for something not to be the case. However, these examples only show what is the case, not what must be the case. These are called contingent or synthetic truths.

Exercise

Put "Yes" next to the following statements that are logical or empirical necessities, or put "No" if the statement is logically or empirically impossible. If it is neither, leave the box blank. (NOTE: some statements may have more than one tick or cross - or none at all.)

I have done the first one for you: it is not logically necessary (could not be otherwise) that there is no life on the moon (there might have been) though not logically impossible - so I leave the Logical box blank. Empirically, we know there isn't (as far as I know), so I put "Yes" in the Empirical box.

Statement	Logical	Empirical
There is no life on the moon
All cows eat grass
All humans are mortal
Some pigs can fly
Children are younger than their parents
The rain in Spain stays mainly in the plains
Dave likes red wine
2 + 2 = 5
The Sun is round
God is good
The devil is good

How did you do? Click here to have a look at my answers and compare them with your own.

You will have noticed that whether something is logically or empirically necessary, or impossible, will depend on a range of complex issues. Therefore, my answers are by no means the only ones. The question of whether God exists, for example, depends on your concept of God or whether in fact you believe He exists (this is the question of empirical necessity).