When Thomas Boston talked about the Christian’s duty to love God, he said that we need to know God in order to truly love him. But Boston was careful to explain this knowledge by using a great phrase: “Comprehend him ye cannot, but apprehend him ye must, as he has revealed himself.” Richard Muller summarizes this doctrine well in volume three of Post-Reformation Reformed Dogmatics:
God is not known through his essence – but “through his effects and his names, by which he wills to reveal his virtues to us” (Cocceius, Summa Theol). The nature of God can be known, then, “according to the manner of divine Revelation, and the measure of our knowledge” and is to be discussed in terms of the name of God and in terms of the definition (Ibid.).
The exposition of doctrine, moreover, proceeds on the premises that whatever is said or predicated of God is not God himself – for God is ineffable – but rather what the human mind in its limitation can apprehend about God. Indeed, a distinction must be made between “comprehension” and “apprehension,” inasmuch as we cannot have an “adequate” idea of God in the sense that we know and understand God fully or are able “fully to describe” the divine perfections, but we can have “some imperfect or inadequate ideas of what surpasses our understanding and we can have “a full conviction that God hath those infinite perfections, which no creature can comprehend” (Ridgley, Body of Divinity)
Thus, language about God proceeds cautiously, frequently according to a negative manner; as when God is called “incomprehensible” or “infinite.” These identifications of God are intended to “remove far from him the imperfections of creatures” (Trelcatius, Scholastic Methods).
In other words, our human minds are limited, darkened by sin, and finite. Therefore we cannot fully comprehend God nor can we perfectly describe and explain him. Even our best theology is imperfect. However, because he has revealed himself (in creation but more specifically in his Word and in Jesus), we can apprehend him and know him in a true and saving way. It’s not because we deserve it or because we’re smart, super intelligent, or supremely wise. It’s because he is gracious. It is his good pleasure to reveal himself to his people and give them the hearts to believe his Son (cf. Matt. 11:27, Luke 10:22, & 2 Cor. 4:6)!