The necessary tools

Pictures speak a thousand words. Imagine a pair of eyeballs and ears dangling from the sides, and you can argue that organs need to be fed etc, but these are the two most important "tools" you need in language learning. One of them, namely the backbone, needs to be taken metaphorically. Incidentally, did you know that language learning and metaphorical use of language are considered excellent mental exercises which may be beneficial for warding off and offseting certain debilitating diseases? One example of this can be found here