Taking the word in the proper sense of denoting Him, we shall describe God — who cannot be defined, inasmuch as He “surpasses every essence and is incomprehensible” — from the various descriptions of Him apparent throughout Scripture and collected together (Exod 34:6, etc.; Deut 10:17; Rev 4:8; Acts 17:24, etc.; 1 Cor 8:4,5,6; 1 Tim 1:17, and 6:15,16): He is a spiritual essence, entirely simple and infinite, that is eternal and immeasurable, and immutable; living and immortal, understanding, wise and all-knowing. He is goodness itself, love, kindness, mercy, forbearance, righteousness, and holiness, etc. He is one in essence, but three in persons: the Father who has brought forth the Son from eternity; the Son who is born of the Father; the Holy Spirit, who proceeds from the Father and the Son, who even proceeds from the Father through the Son. He is the Creator, the Preserver, and the Ruler of the universe, the Redeemer, Savior and the Glorifier of his elect.

This description of God comprises three parts: the revelation of the one Essence by means of various attributes; the enumeration of the divine Persons; and the revelation of his deeds.

Synopsis of a Purer Theology, Disputation 6 Paragraphs 17 & 18.