In particular, similarly to Smalltalk and differently for example from C++, Objective-C does method dispatching from empty interfaces and has does-not-understand functionality.

Everything Is An Object in Smalltalk, and of course this can't be true in Objective-C due to its mixed heritage.

in smalltalk you are always running inside of a live system, so if you made a mistake its immediate that it happened right then and there, but in obj-c its a code-build-run environment so the place you changed and the state you have to progress to to exercise that change are far away and you might not catch it until runtime / in the field.