Question: All rational thought and past scientific findings seem to point to a causaly determined universe based upon past states of the universe and the laws of nature. In your response you claimed that it is readily apparent to those who have free will that they do. This does not seem to be a rational explanation of the topic to me. It seems to me that most Objectivist claims are based against feeling and intuition, and more on studied thought.
Answer: That we have free will is self-evident. You chose to write this question. Indeed, most fundamentally, you chose to think about it. This is not an appeal to intuition. It is an appeal to a fact we experience all the time. No more would it be intuition to say that the sun shines, or to make any number of other commonplace observations. People choose, and they can choose to think or not to think. We know it, because we do it.
If you aren't aware that you are choosing, and that you control your level and direction of mental focus, I am afraid I could not possibly offer any further evidence for it. You will provide yourself with the evidence as you determine what response to make.
I can, however, try to put your mind at ease. I don't know what you make of quantum indeterminacy, or the direction of human history, but in either case we have real phenomena that do not arise deterministically from the "past state of the universe." It is true that modern science has achieved some magnificent and powerful theories of physical nature by assuming that determinism was true for the objects under study. But no deterministic explanation exists for the phenomena I mentioned, and there are good reasons to think there never will be one (namely, our understanding of sub-atomic particles and our awareness of free will). Deterministic reductionism is a myth of the scientific community, not an established fact. The fact of free will does not oppose the doctrines of science; rather, it is simply a fact that science is trying to come to grips with through disciplines like cognitive science, psychology, and economics.
If you are interested in learning more about the Objectivist view of free will, let me recommend two products of David Kelley's: his lectures on free will in his "Foundations of Knowledge" tapes and his discussion of free will vs. determinism in his course " Perennial Questions of Objectivism ."