Bacon on Human Understanding

"For no one successfully investigates the nature of a thing in the thing itself; the inquiry must be enlarged so as to become more general" - Aphorism 70

This excerpt from The New Organon struck me as strange, specifically because Bacon lists qualities and tendencies of human understanding in preceding and succeeding aphorisms. If we are to accept that the nature of a thing cannot be well observed by the thing itself then what do we make of his claims about human understanding? Maybe Bacon would not consider his claims to be successful at mining the nature of human understanding but rather helpful in knowing how it seems to behave or interact with the environment. He does not say that his observations are a result of some sort of experiment, so I am willing to accept them as speculations and move on.