If a person lacks yirah (fear and awe of heaven) and deep intent in his mitzwah performance, than he will not be able to connect to the highest will of HaShem. Without this yirah and hitbonenut, his mitwah performance will be just as physical/corporeal as he is. Likewise, without the physical performance of the mitzwah, all his yirah and hitbonenut will not connect man to HaShem at all.
The proof he offers is this: Shlomo haMelech who was wiser than all men, when he went to act against the mitzwah, (and took many wives) no matter his great wisdom and lofty intent, he failed.
How does he relate this to Noah? He explains that Noah was especially careful in his kiyyum of the mitzwah peru u'revu (be fruitful and multiply) and through this mitzwah with deep intent he was able to connect to HaShem and all the other mitzwoth. This is why Noah is called a Tzaddik, complete in his generations.