What can Mason eat?

Mason has been crawling now for a couple of weeks, and the things that really get him moving are Tyler's Crocs. Mason first crawled across the entire kitchen just to get to those rubbery, chewy shoes. So, one afternoon, I put Mason down in the middle of the living room, in the middle of his toys and then I went into the kitchen. A few minutes later, Mike walked in and must have noticed that Mason had crawled to the hallway to Tyler's Crocs and was chewing on one. Mike asked me, "Are we letting Mason eat shoes?"
Me: (pause) Would you let him eat gravel? Or dirt? Where have your shoes been? Would you let him eat that?
Mike: (I'm sure there's eye-rolling that I didn't see) A simple 'no' would have sufficed.