The point of a reaction paper is to help you develop the ability to state and analyze arguments. To this end, a reaction paper should typically have three paragraphs. In the first, you want to provide some context for the argument you are choosing to analyze -- explain why the philosopher is making the argument, what is the point of doing so? In the second, state the argument. Identify the premises and the conclusion of the argument. In the third paragraph, analyze the argument. You do this by evaluating the premises (are they true or false? why?) and the reasoning (does the conclusion follow from the premises, or might the premises be true and still the conclusion false?).

Sample:

In the First Meditation, Descartes wonders whether he has any beliefs that cannot be doubted. He is concerned that many of his beliefs may be false, and that he is unable to distinguish the true ones from the false ones. Accordingly, he attempts to doubt all his beliefs, hoping to find some that cannot be doubted and so must be true. Descartes thinks that he can then use these true beliefs to justify still more. One argument he considers for doubting his beliefs is the dreaming argument.

Although the dreaming argument can be interpreted in various ways, I interpret as follows:

1) Beliefs we form while dreaming are unjustified.

2) But we cannot know whether we are awake or dreaming.

Therefore we cannot know whether any of our beliefs are justified.

I believe that Descartes' argument is valid. If the premises are true, the conclusion follows. But are the premises true? The first is. I have formed all sorts of beliefs while dreaming, such as that Ingrid Bergman has asked me to marry her, but upon awakening I recognize immediately that the belief is false. This shows that beliefs I form while dreaming cannot be trusted. The second premise, however, does not seem as certain as the first. I believe that dreamed experiences have a character that is not exactly like the character of experiences I have while awake. Objects in my dreams move around in ways that they don't seem to do when I'm awake. They change colors in strange ways. Time in my dreams doesn't move at a regular pace -- it speeds up and slows down. Because the world I experience in my dreams is not like the world I experience when awake, I think we can know whether we are awake or dreaming. Thus, I believe the second premise of the dreaming argument is false, and so the conclusion of the argument may not be true.