Spinoza's Ethics: I.P23: Infinite Modes

Here Spinoza ties together the prior two propositions in this difficult transition from God and God's existence (prior to P21) to God's modes. If everything can be stated as substance (that which is in itself) and modes (that which is in another), somethings are not clearly in one or the other. In P21, Spinoza addresses the example of the idea of God in thought. On closer scrutiny, it is difficult to distinguish the attribute of thought from the seeming mode which is the idea of God in thought. He articulates this relationship between substance and mode as immediate or "immediately." In P22, Spinoza addresses the example of motion and rest (as a form of measuring) in extension. Again, it is difficult to separate the two. Importantly, modes are "conceived" while attributes are "perceived." He articulates this relationship between substance and mode as mediante or "mediating."

Omnis modus qui et necessario et infinitus existit, necessario sequi debuit vel ex absoluta natura alicujus attributi Dei vel ex aliquo attributo modificato modificatione quae et necessario et infinita existit. 

Translated as,

Every mode which exists necessarily as infinite necessarily had to follow either from the absolute nature of some attribute of God, or from some attribute measured by a measurement which exists necessarily as infinite.

Demonstratio: Modus enim in alio est per quod concipi debet (per definitionem 5) hoc est (per propositionem 15) in solo Deo est et per solum Deum concipi potest. Si ergo modus concipitur necessario existere et infinitus esse, utrumque hoc debet necessario concludi sive percipi per aliquod Dei attributum quatenus idem concipitur infinitatem et necessitatem existentiae sive (quod per definitionem 8 idem est) aeternitatem exprimere hoc est (per definitionem 6 et per propositionem 19) quatenus absolute consideratur. Modus ergo qui et necessario et infinitus existit, ex absoluta natura alicujus Dei attributi sequi debuit hocque vel immediate (de quo vide propositionem 21) vel mediante aliqua modificatione quae ex eius absoluta natura sequitur hoc est (per propostionem praecedentem) quae et necessario et infinita existit. Q.E.D.

Translated as,

For a mode is in another, through which it must be conceived (by D5), that is (by P15), it is in God alone, and can be conceived through God alone. So if a mode is conceived to exist necessarily and be infinite, it necessarily ought to be concluded or perceived as such by some attribute of God insofar as that same attribute is conceived to express infinity and necessity of existence, or (what by D8 is the same thing) eternity, that is (by D6 and P19) insofar as it is considered absolutely. Therefore, the mode which exits necessarily and is infinite, has had to follow from the absolute nature of some attribute of God, either immediately (about which see P21) or by some meditating measurement, which follows from its absolute nature, that is (by the preceding proposition), which exists necessarily and is infinite.