I didn't call the Vedas speculative. I called them a part of all that is. Because they are. They aren't everything that exists, and thus they do not contain all that exists. Regarding speculation, interpretation of reality using a single source--whatever that source may be--is indeed speculative in nature. Thus it is the speculation of a human being regarding the nature of reality to draw upon the Vedas and the Vedas alone as a basis for the total description of how reality functions. It is impossible to understand one thing without first understanding all things.
RE: The True Theory of Everything: Link Compilation