Well, at least that is one of the claims in the book "I Don't Have Enough Faith to be an Atheist" by Norman Geisler and Frank Turek. Many of you should know of this book as it is the focus of my Evidence thread in the History Forum. The book says this on page 129.
"...if materialism is true, then reason itself is impossible. For if mental processes are nothing but chemical reactions in the brain, then there is no reason to believe that anything is true (including the theory of materialism). Chemicals can't evaluate whether or not a theory is true. Chemicals don't reason, they react.