Was sin necessary for knowledge?

[John V]

It seems as though moral knowledge would be required to sin, though, 

Paul says that Eve was deceived, but Adam wasn't. If Adam wasn't deceived, it would seem that he did have moral knowledge prior to eating. Also, he says that sin entered the world through Adam, even though Eve ate first. 

Applying this to Gen 3, it seems that Adam gained moral knowledge prior to eating - possibly from observing and considering Eve's action. He then consciously chose to sin, possibly out of fear of losing Eve.