The both statements you have quoted are still valid. Moreover, if you would think a bit you would realize that the world around you is duck-typed. At least at

The both statements you have quoted are still valid. Moreover, if you would think a bit you would realize that the world around you is duck-typed. At least at the level of proteins. One more thing. Every ontological attempt to use naive categories would fail and end up in duck-typing-like approach, because it reflects how the mother nature is.