Validity vs Soundness

Argument conundrum:
There are certain principles, such as the principle that no object can both exist and not exist at the same time, that everyone agrees to. The only explanation for why we all agree to these principles is that we are all born knowing them. Thus, we are all born knowing certain principles.

I got this question in a university exam and I said it is invalid, since if falls prey to the fallacy of begging the question. I got the question wrong.
Is this argument valid and sound?
Any help and analysis would be greatly appreciated.