Greatly begin. Though thou have time, but for a line, be that sublime. Not failure, but low aim is crime.

The lines urge immediate, ambitious action: begin boldly, even if you can only manage a small effort (“but for a line”), and make that small effort worthy (“sublime”). The moral emphasis falls not on the inevitability of setbacks but on the ethical failure of aiming too low—treating mediocrity or timidity as the real “crime.” In this sense, the quote frames aspiration as a duty: one’s limited time or capacity is not an excuse for trivial work, because greatness can be pursued in miniature as well as in large undertakings. It is a compact exhortation to high standards, courage in starting, and seriousness of purpose.