How is it that we can know anything about the God whose very thoughts are higher than our thoughts? (Isaiah 55:9) The answer? Revelation. (The doctrine, not the book–though we do learn about him in the book.) We can only know God to the extent that he has made himself known.
So how is it that God has revealed himself to us? Here are some helpful thoughts from Herman Bavinck on the matter:
The revelation that thus comes to us objectively from the side of God is to be differentiated into a general sense and a special one. General revelation is that conscious and free act of God by which, by means of nature and history (in the broadest sense, hence including one’s own personal life experience), he makes himself known–specifically in his attributes of omnipotence and wisdom, wrath and goodness–to fallen human beings in order that they should turn to him and keep his law, or, in the absence of such repentance, be inexcusable.
Special revelation, in distinction from the above, is that conscious and free act of God by which he, in the way of a historical complex of special means (theophany, prophecy, and miracle) that are concentrated in the person of Christ, makes himself known–specifically in the attributes of his justice and grace, in the proclamation of law and gospel–to those human beings who live in the light of this special revelation in order that they may accept the grace of God by faith in Christ or, in case of impenitence, receive a more severe judgment. Both this general and this special revelation are primarily objective; and included in this objective special revelation, accordingly, is the revelation that occurs in the consciousness of prophets and apostles by addressive and interior speech, by divine inspiration in the sense of 2 Timothy 3:16.
Corresponding to this objective revelation, general as well as special, there is a subjective revelation, which in a broad sense can be called revelation but for the sake of clarity can be better described as illumination. Answering to this objective general revelation, there is an illumination of the Logos (John 1:9), or of the Spirit of God, in intellect, conscience, heart, and mind of human beings, such that they can understand God’s general revelation in nature and history. Likewise, answering to this objective special revelation, there is an illumination of human beings who live in the light of the gospel, by the Spirit of God, such that they can recognize and know the special revelation that comes to them in Christ and more specifically in Scripture as special revelation of God.
(Reformed Dogmatics, vol. 1, p. 350)
To make that more concise:
God’s revelation in creation (general revelation), making known his eternal attributes, is given to all “so that men are without excuse” (Romans 1:18-20). God’s revelation in the Word (special revelation), referring both to the person and work of Jesus Christ (the eternal Word) and canonical Scripture (the inspired and written Word), makes known his law and gospel, justice and grace. These are standard categories in Christian theology.
What I appreciate is Bavinck’s reminder of the third “facet” of revelation: the inward work of the Spirit to open our eyes and minds and hearts to the things of God. Apart from this, we cannot rightly understand either God’s general or special revelation, because our minds remained darkened and our hearts hardened.
The Spirit works to remove our hearts of stone and give us hearts of flesh (Ezekiel 36:25-27), and shine into our hearts “to give us the light of the knowledge of the glory of God in the face of Christ” (2 Corinthians 4:6). It is this action that convinces us that Scripture–and its witness to Jesus Christ–is indeed God’s revelation. This work is what theologians refer to as testimonium internuum spiritu sanctu (the internal testimony of the Holy Spirit), which Bavinck is right to call a kind of subjective revelation.
In short, how can we know the God whose ways and thoughts are higher than our ways and thoughts? Through his revelation, which he accomplishes objectively in creation and Scripture and subjectively in the Spirit’s work to illumine our hearts and minds so that we recognize who we encounter in creation and Scripture.