If the power to do hard work is not a skill, it’s the best possible substitute for it.

The line contrasts innate “skill” with the cultivated capacity for sustained effort. Garfield’s point is that even when talent or specialized ability is lacking, disciplined hard work can function as a practical stand-in—often producing comparable results through persistence, repetition, and reliability. Implicitly, it also reframes “hard work” as a kind of meta-competence: the ability to apply oneself steadily is itself valuable capital, especially in education, public life, and professional advancement. The aphorism fits a broader nineteenth-century American ethic that praised self-improvement and industriousness, suggesting that character and effort can compensate for limitations in aptitude.