By.
Synonyms:
by dint of, by means of, through, with.
By refers to the agent; through, to the means, cause, or condition; with, to the instrument. By commonly refers to persons; with, to things; through may refer to either. The road having become impassable through long disuse, a way was opened by pioneers with axes. By may, however, be applied to any object which is viewed as partaking of action and agency; as, the metal was corroded by the acid; skill is gained by practise. We speak of communicating with a person by letter. Through implies a more distant connection than by or with, and more intervening elements. Material objects are perceived by the mind through the senses.