Spinoza's Ethics: I.D2: Finitude

In I.D2, Spinoza carefully defines something as finite "in its own kind." For anything to have limits, these limits are created jointly, not unilaterally. There needs to be something or somethings at all limiting points. For this something (or collection of somethings) to jointly create a limit outside of the primary thing itself, the outsidedness must be greater than that insidedness.

Ea res dicitur in suo genere finita quae alia ejusdem naturae terminari potest. Exempli gratia corpus dicitur finitum quia aliud semper majus concipimus. Sic cogitatio alia cogitatione terminatur. At corpus non terminatur cogitatione nec cogitatio corpore.

Translated as:

That thing is said to be finite in its own kind that can be limited by another of the same nature. For example, a body is called finite because we always conceive another that is greater. Thus a thought is limited by another thought. But a body is not limited by a thought nor a thought by a body.