Following directly from my last post, I can be certain of at least two things:
1) Everything that we think (ideas) or experience (what we perceive) exists to some capacity.
2) There's no way of knowing the exact (or type of) capacity. (perhaps everything is pure idea)
The computer screen in front of me exists to some extent. Is it a material object that exists objectively, outside my thoughts and perceivances or is it just an idea? I don't know, but it certainly exists!
Okay, I think I can lump this idea into one bullet point: Everything we think of, experience, or perceive exists - but there is no way of knowing to what capacity.
That is a pretty general statement, but it is also pretty solid (in my opinion) in terms of certainty.
So what else can you be certain of? I have provided one thing that I believe to be certain. Descartes was a foundationalist; in essence his whole philosophy was built upon his first meditations - his basic 'foundation' was that since he thinks, he exists. This is the first conclusion he came to - therefore that was his foundation. What I did was similar, but I don't know if I would call it a foundation. In any case, if we can think of anything else we can be certain of, everything must agree and not be contradictory.
The first thing that came to mind is human feelings. Right now I feel happy. Am I certain I feel happy? How the heck could I not be certain that feel happy? I suppose we could follow from our first certainty conclusion. To feel happy is to experience joy. The joy necessarily exists to some extent, to some capacity. The joy exists since we experience it, therefore we feel happy. It is certain!
Even if there is an 'evil god' or 'evil genius' controlling our thoughts in a way that makes us feel happy, but we really aren't. We experience happiness nonetheless. Therefor we are certainly happy at that instant! Let's add it to the list.
1) Everything we think of, experience, or perceive exists - but there is no way of knowing to what capacity.
2) Emotional feelings are certain at the instant they are felt.
You may be thinking that we could just modify 1) to include 2) saying that whatever we experience exists and is certain, but we can't say this! We have to be careful.