Spinoza's Ethics: II.P21

Here Spinoza reaches the sense that occurs in meditation or reflective thought. At times we think simply as the mind connected to the body or sensation or object. However, he outlines that the same connection can occur when the mind is connected to the mind and reflects on cognition itself. The form of the idea allows for that idea as such to become the idea of the mind, or the idea of the idea.

Hæc mentis idea eodem modo unita est menti ac ipsa mens unita est corpori.

Translated as,

This idea of the mind is united in the the same way to the mind as the mind itself is united to the body.

DEMONSTRATIO: Mentem unitam esse corpori ex eo ostendimus quod scilicet corpus mentis sit objectum (vide propositiones 12 et 13 hujus) adeoque per eandem illam rationem idea mentis cum suo objecto hoc est cum ipsa mente eodem modo unita esse debet ac ipsa mens unita est corpori. Q.E.D.

Translated as,

That the mind is united to the body from this we show because just as the body is the object of the mind (see IIP12 and 13) to such a degree by that same reasoning the idea of the mind with its own object that is since by the mind itself in the same way ought to be united as the mind itself is united to the body.

SCHOLIUM: Hæc propositio longe clarius intelligitur ex dictis in scholio propositionis 7 hujus; ibi enim ostendimus corporis ideam et corpus hoc est (per propositionem 13 hujus) mentem et corpus unum et idem esse individuum quod jam sub cogitationis jam sub extensionis attributo concipitur; quare mentis idea et ipsa mens una eademque est res quæ sub uno eodemque attributo nempe cogitationis concipitur. Mentis inquam idea et ipsa mens in Deo eadem necessitate ex eadem cogitandi potentia sequuntur dari. Nam revera idea mentis hoc est idea ideæ nihil aliud est quam forma ideæ quatenus hæc ut modus cogitandi absque relatione ad objectum consideratur; simulac enim quis aliquid scit, eo ipso scit se id scire et simul scit se scire quod scit et sic in infinitum. Sed de his postea.

Translated as,

This proposition is understood by far more clearly from statements in the IIP7S; for there we show the idea of the body and the body that is (by IIP13) the mind and the body are one and the same to be indivisible because it is conceived at one time under the attribute of thought and at another under the attribute of extension; wherefore the idea of the mind and the mind itself are the same thing is a thing which of course is conceived under the one and the same attribute of thought. I say the idea of the mind the the mind itself in God follow to exist by the same necessity from the same power of thinking. For actually the idea of the mind that is the idea of the idea is nothing other than the form of the idea insofar as this as a way of thinking and is considered away from the relationship to its object; and at the same time anyone might know anything, in this way itself knows itself that it knows it and at the same time knows that it knows because it knows and on to infinitum. But later on these things.

Spinoza's Ethics: II.P20

Mentis humanæ datur etiam in Deo idea sive cognitio quæ in Deo eodem modo sequitur et ad Deum eodem modo refertur ac idea sive cognitio corporis humani.

Translated as,

The idea of the mind of a human is also given in God or the understanding which follows in God in the same way and refers to God in the same way as the idea or understanding of the human body.

DEMONSTRATIO: Cogitatio attributum Dei est (per propositionem 1 hujus) adeoque (per propositionem 3 hujus) tam ejus quam omnium ejus affectionum et consequenter (per propositionem 11 hujus) mentis etiam humanæ debet necessario in Deo dari idea. Deinde hæc mentis idea sive cognitio non sequitur in Deo dari quatenus infinitus sed quatenus alia rei singularis idea affectus est (per propositionem 9 hujus). Sed ordo et connexio idearum idem est ac ordo et connexio causarum (per propositionem 7 hujus); sequitur ergo hæc mentis idea sive cognitio in Deo et ad Deum eodem modo refertur ac idea sive cognitio corporis. Q.E.D.

Translated as,

An understanding of God is (by IIP1) is an idea in God to such a degree (by IIP3) so much of it as much of all of its affections and consequently (by IIP11) of the mind of a human must be given by necessity. Next this idea of the mind or understanding does not follow to be given in God insofar as it is infinite but insofar as another idea of a singular thing is an affect (by IIP9). But the order and connection of the ideas are the same as the order and connection of the causes (by IIP7); therefore it follows that this idea of the mind or understanding in God and refers to God in the same way and the idea or understanding of the body.

Spinoza's Ethics: II.P19

As Spinoza articulates the ability of the mind to understand the human body, he is also explaining how the human mind is subject to illusions. The human mind has direct connection with ideas of modifications of the body. This ideas are initially non-representative. In our parlance, we call these feelings. These modifications of the human body are true in themselves but we do not understand them in a cause effect way. This is, in our terms, subjective rather than objective knowledge. 

Insofar as God understand the human body, the idea is true and Spinoza describes how this is structured through the ideas of other singular things with clarity about causal connections. For us to understand the human body as God does, or even to move in that direction, means a better understanding of causal connections. While science provides some help, Spinoza's earlier propositions about God explore the critical role of necessity as manifesting true causal connections.

As a result, to make decisions with more reality or perfection or God - all of which are the same here - we can simply allow necessity to reveal itself as this force shows true causal connections. We can all identify those times where we called someone to just share a conversation or a recent event and found ourselves surprisingly hurt. Rather than making a call out of "necessity," we made the call "voluntarily." But this voluntary action was typically rooted in a subconscious desire for affirmation. When that subconscious desire was not met, we are suddenly disappointed. "Necessity" would have indicated two things: 1) don't make the call and 2) meet the subconscious desire by ourselves - leading to more power and an increase in perfection - which are the same here.

Mens humana ipsum humanum corpus non cognoscit nec ipsum existere scit nisi per ideas affectionum quibus corpus afficitur.

Translated as,

The human mind does not understand the human body itself and does not know that it exists unless by the ideas of modifications by which [the mind] is affected.

DEMONSTRATIO: Mens enim humana est ipsa idea sive cognitio corporis humani (per propositionem 13 hujus) quæ (per propositionem 9 hujus) in Deo quidem est quatenus alia rei singularis idea affectus consideratur vel quia (per postulatum 4) corpus humanum plurimis corporibus indiget a quibus continuo quasi regeneratur et ordo et connexio idearum idem est (per propositionem 7 hujus) ac ordo et connexio causarum, erit hæc idea in Deo quatenus plurimarum rerum singularium ideis affectus consideratur. Deus itaque ideam corporis humani habet sive corpus humanum cognoscit quatenus plurimis aliis ideis affectus est et non quatenus naturam humanæ mentis constituit hoc est (per corollarium propositionis 11 hujus) mens humana corpus humanum non cognoscit. At ideæ affectionum corporis in Deo sunt quatenus humanæ mentis naturam constituit sive mens humana easdem affectiones percipit (per propositionem 12 hujus) et consequenter (per propositionem 16 hujus) ipsum corpus humanum idque (per propositionem 17 hujus) ut actu existens; percipit ergo eatenus tantum mens humana ipsum humanum corpus. Q.E.D.

Translated as,

For the human mind is the idea itself or the understanding of the human body (by IIP13) which (by IIP9) is in God indeed insofar as another idea of a singular thing is considered an affect or because (by Postulate 4) the human body lacks many bodies by which continuously as if it is regenerated and the order and connection of ideas is the same (by IIP7) as the order and connection of causes, will be this idea in God insofar as it is considered an affect by the ideas of more singular things. Thus God has the idea of the human body or understands the human body insofar as [God] is an affect by some more ideas and not insofar as [God] constitutes the nature of the human mind that is 9by IIP11C) the human mind does not understand the human body. But the ideas of the modifications of the body are in God insofar as [God] constitutes the nature of the human mind or the human mind perceives those modifications (by IIP12) and consequently (by IIP16) the human body itself and it as actually existing; thus [God] perceives the human mind so long as the human body.