Meditations 3.13

As physicians have always their instruments and knives ready for cases which suddenly require their skill, so do thou have principles ready for the understanding of things divine and human, and for doing everything, even the smallest, with a recollection of the bond which unites the divine and human to one another. For neither wilt thou do anything well which pertains to man without at the same time having a reference to things divine; nor the contrary.

Marcus Aurelius, Meditations 3.13, translated by George Long

Just as physicians always keep their lancets and instruments ready to their hands for emergency operations, so also do thou keep thine axioms ready for the diagnosis of things human and divine, and for the performing of every act, even the pettiest, with the fullest consciousness of the mutual ties between these two. For thou shalt never carry out well any human duty unless thou correlate it to the divine, nor the reverse.

Marcus Aurelius, Meditations 3.13, translated by C. R. Haines