This is a hard fold - I don't know if I could make it. Although it must be said, if he's truly that LAggy, his check on the flop is suspicious as hell. This type of player is almost always looking to win the pot early, so I get nervous when they do something other than that. I pretty much agree with the previous post - play this faster and you'll get your money in anyway, and lose here anyway. I'd bet 1/2 pot behind him on the flop and raise if he led the turn. If he check-raised the flop the money is going in before the turn without a doubt.