[cjfd]

Duck typing. If it quacks like a duck and swims like a duck it might be a duck. But it might also be a nuclear submarine doing a duck impersonation. The question is whether you want a nuclear submarine in your pond.

[marcosdumay]

The philosophy of duck typing is very clear in that yes, you should accept a nuclear submarine in your pound.

The problems are that you won't remember to do the same exact checks everywhere and document them.