On page 93, Loftus says "There are four assumptions of science: 1) The belief of an external world independent of the perceiving subject as the basis of all natural science . . . 2) The intelligibility of nature . . . 3) The uniformity of nature . . . 4) The adequacy of scientific language and math to adequately describe the world." Now, I agree with these claims. I am an empiricist (meaning I believe that all knowledge is derived from the physical world). But I think that it is my belief that all physical things are material/immaterial compositions that allows for all these beliefs. Let me explain.
You see, for the materialist, there are no immaterial objects. Only physical objects and physical processes. Now, it is because they believe this that I think that they cannot affirm these points. First, the assumption number one is fine. There is no reason that this cannot be assumed. But assumption number two is a problem. I'll explain.
First, a rational assumption is one where there seems no reason to deny the claim, but it remains difficult, if not impossible to prove. But I think that there is good reason to deny this claim, given a materialist metaphysic. You see, if all external reality is purely matter, then the object of one's knowledge is not at all identical to the object in reality. The object in one's knowledge would be identical to whatever chemicals, electric pulses, and whatnot are involved in the act of the thought. But the object in reality is not identical to those factors; it is identical to whatever elements, compounds, accidents, and characteristics of extension that it maintains. In fact, if one were to line up all the characteristics of either object next to one another, they would find that they share not a single one in common.
This means that, of everything we know about the two objects, they are wholly different from one another. So is it even rational to assume that the objects are even similar? No. There is too much of a reason to doubt it. Thus there is good reason to deny the intelligibility of nature. But then assumptions three and four are worthless. Therefore, the materialist is left with assumption number one, which now is nothing but an article of blind faith. So science, if it is considered to be knowledge of all physical reality, is incompatible with materialism, since no physical reality may really be known.
So how do I avoid this? Well, it is my position that the only way to explain sameness through change (which includes the sameness of an object in reality to a changed state in my mind) is to postulate an immaterial aspect to all reality. Now this is not a mere assumption, since sameness through change is demonstrable (for instance, I am the same person that I was 20 years ago, and that is rationally undeniable--but none of the physical elements of me are the same). Therefore, belief in a material/immaterial composition is necessary for science and is such a belief is demonstrable and thus not ad hoc.