When you do use the first person, justification for your assertions should be offered. The fact that you believe something to be the case is of little philosophical relevance unless you also give your reader a good reason for believing what you do too. The goal of a philosophy paper is to, as for as possible, get at the truth. There is no guarantee that one individual's intuitions on a particular matter are truth conducive. When arguing a point, remember that repeating a proposition over and over again, even if it is worded slightly differently each time, does nothing to make the point more persuasive.
Repetition is simply a waste of space.
It is also important to be careful with your use of conclusion marker words and phrases such as 'thus', 'hence', 'therefore', 'it follows that' and so on. These words and phrases should only be used when you wish to indicate the conclusion of an argument or a sub-argument. When using the, be sure to carefully check that the conclusion you wish to draw really does follow from the premises that you have put forward. Finally, above all, use common sense when writing papers.