[WildHorseCrash]

Is there something inherently wrong with, or unscientific about, an a priori assumption?

It depends. If you are asserting a scientific statement and the a priori assumption is not, itself, scientific, then, yes, there is something inherently wrong with it. Otherwise the statement, "Assume that Zeus created the Earth. The Earth exists. Therefore, I have proved the existence of Zeus." would be scientifically sound.

[Fester Chugabrew]

Is the a priori assumption that matter behaves, and will continue to behave, according to specific and established patterns and properties an unscientific assumption?

[Fester Chugabrew]

I'm trying to think of the last occasion where proponents of intelligent design invoked the name of Zeus as a scientific entity. Would you please supply an example?