Literal and Figurative Language
If you speak as though being understood were your primary concern, then you can only say common things. For language, insofar as it is a tool of clear and straightforward communication, is by definition common, which is to say it is limited to common meanings. Nothing uncommon may be said by common means, unless those means are explicitly used against their primary function, or more precisely by making their primary function secondary. Common words must be employed in such a way that their common meanings are reduced to the secondary (but necessary) status of a portal, inviting the reader or listener toward the uncommon thoughts hidden within their new employment.
It is in this way that Heraclitus, Plato, and Rousseau were right — and Lucretius, Hobbes, and Locke wrong — in their various manners, about the mechanism of language development. Language, to the extent that it remains vital and vibrant as an instrument of intellectual growth and societal improvement, must never be allowed to calcify into a repository of “literal meanings,” as modern rationalism would have it. Figurative speech is not a secondary or decorative appendage of language, pleasant but unnecessary. On the contrary, a fully human language will and must be essentially, primarily, definitively figurative in nature. In language development, the literal naturally follows upon the figurative, as the weaker sister, the common meaning established by simplifying and regulating the figurative — by sapping it of its vitality, in the names of clarity and straightforwardness.