The fact is, that Sherlock, and (for aught I know) Gregory Nyssen, had not the clear idea of the Trinity, positively; but only a negative Arianism.
Ib.p.

127.
He proceeds to shew that this unity is without all manner of confusion and mixture, * * for the mind that loves, is in the love.

* * * And the knowledge of the mind which knows and loves itself, is in the mind, and in its love, because it loves itself, knowing, and knows itself loving: and thus also two are in each, for the mind which knows and loves itself, with its knowledge is in love, and with its love is in knowledge.
Then why do we make tri-personality in unity peculiar to God?
The doctrine of the Trinity (the foundation of all rational theology, no less than the precondition and ground of the rational possibility of the Christian Faith, that is, the Incarnation and Redemption), rests securely on the position,--that in man 'omni actioni praeit sua propria passio; Deus autem est actus purissimus sine ulla potentialitate'.

As the tune produced between the breeze and Eolian harp is not a self-subsistent, so neither memory, nor understanding, nor even love in man: for he is a passive as well as active being: he is a patible agent.
But in God this is not so.

Whatever is necessarily of him, (God of God, Light of Light), is necessarily all act; therefore necessarily self-subsistent, though not necessarily self-originated.