This line appears in Ralph Waldo Emerson's Self-Reliance:
Man is explicable by nothing less than all his history.
I have been told that in order to express generality, one should use the definite article if the noun is singular. In this case it should be "the man", rather than just "man".
And often they are in plural form like this example:
Words are the foundations of a language.
What if I re-wrote the sentence to use the singular form, as Emerson might?
Word is the foundation of a language.
When should a word be singular and when should it be plural in expressing generality?