Ethics was a literary work by Benedict de Spinoza, published in 1677.
Gary Mitchell and James Kirk considered this reading to be "longhair stuff", but after encountering the galactic barrier and being infused with psionic energy, Mitchell found this complicated work to be much simpler as he viewed it on a reader screen.
When Mitchell discussed Spinoza with Kirk in sickbay, he was reading Part IV, the proof of Proposition XXXVII, which states: "The good which every man, who follows after virtue, desires for himself he will also desire for other men, and so much the more, in proportion as he has a greater knowledge of God". (TOS: "Where No Man Has Gone Before")