On The Holy Trinity by St. Augustine
Chapter 5.--That These Three are Several in Themselves, and Mutually All in All.
8. But in these three, when the mind knows itself and loves itself, there remains a trinity: mind, love, knowledge; and this trinity is not confounded together by any commingling: although they are each severally in themselves and mutually all in all, or each severally in each two, or each two in each. Therefore all are in all. For certainly the mind is in itself, since it is called mind in respect to itself: although it is said to be knowing, or known, or knowable, relatively to its own knowledge; and although also as loving, and loved, or lovable, it is referred to love, by which it loves itself. And knowledge, although it is referred to the mind that knows or is known, nevertheless is also predicated both as known and knowing in respect to itself: for the knowledge by which the mind knows itself is not unknown to itself. And although love is referred to the mind that loves, whose love it is; nevertheless it is also love in respect to itself, so as to exist also in itself: since love too is loved, yet cannot be loved with anything except with love, that is with itself. So these things are severally in themselves. But so are they in each other; because both the mind that loves is in love, and love is in the knowledge of him that loves, and knowledge is in the mind that knows. And each severally is in like manner in each two, because the mind which knows and loves itself, is in its own love and knowledge: and the love of the mind that loves and knows itself, is in the mind and in its knowledge: and the knowledge of the mind that knows and loves itself is in the mind and in its love, because it loves itself that knows, and knows itself that loves. And hence also each two is in each severally, since the mind which knows and loves itself, is together with its own knowledge in love, and together with its own love in knowledge; and love too itself and knowledge are together in the mind, which loves and knows itself. But in what way all are in all, we have already shown above; since the mind loves itself as a whole, and knows itself as a whole, and knows its own love wholly, and loves its own knowledge wholly, when these three things are perfect in respect to themselves. Therefore these three things are marvellously inseparable from each other, and yet each of them is severally a substance, and all together are one substance or essence, whilst they are mutually predicated relatively.