We reason now from facts to conclusion; this is called the inductive method, to collect facts, then draw inferences.

The facts which I have collected on the subject of slavery, in my reading and hearing, lead me to a perfect theory on the subject, and my confidence in that theory is all which it could be if, like you, I were now seeing it verified with my own eyes.
I reason on this subject of slavery, just as our philosophers reason about the moon.

You have learned, dear Aunt, ere this, that there is no water in the moon.

Certain things are observed by our telescopes, in the moon, from which we are sure that there is no water there.

Now there are certain given facts in slavery.