This is Robert Reymond’s analysis of the answer to, ‘What is God?’
The Shorter Catechism begins by employing the phrase ‘a spirit’ to describe God – he is ‘a spirit.’ This phrase is then qualified by three adjectives – ‘infinite, eternal, and unchangeable.’ A prepositional phrase introduced by ‘in’ then modifies the three adjectives; its seven nouns are in turn each qualified by the three adjectives. What this representation intends to show is this: that God is a personal (see the ‘his’) noncorporeal Being who is infinite, eternal, and unchangeable in his being; infinite, eternal, and unchangeable in his wisdom; infinite, eternal, and unchangeable in his power; infinite, eternal, and unchangeable in his holiness; infinite, eternal, and unchangeable in his justice; infinite, eternal, and unchangeable in his goodness; and infinite, eternal, and unchangeable in his truth. This may be depicted as:
Three observations are necessary: First, it is important to note that it is not the first noun per se that distinguishes God absolutely from the creature; angels too are noncorporeal personal beings (Heb 1:14). Nor is it the last seven nouns that distinguish God from the angels or from the human creature; again, they have, or can have, these same characteristics to a certain degree. It is the three adjectives ‘infinite, eternal, and unchangeable’ that distinguish God in the absolute sense from the angels and from the human creature who bears his image; only God possesses these several characteristics in the infinite, eternal, and unchangeable sense.
Second, it is important to underscore the truth that when we speak of God’s ‘infinite, eternal, unchangeable’ being, etc., we are speaking of those attributes that comprise what the Scriptures intend when thy speak of God’s glory. That is to say, God’s glory is the sum total of all his attributes as well as any one of his attributes. For the creature to deny him any one of his attributes is to attack the very glory of God and to deny him that without which he would no longer be God. Or to ascribe to him any attribute which he himself does not expressly claim to have, which ascription can only cancel out some attribute which he does claim to have, is again to represent him as something less than he is and thus is to attack his glory. For this reason it is imperative to listen carefully to God’s description of himself in Scripture.
Third, it should be continually borne in mind that what we affirm here about God we are affirming not only about God the Father but also and equally about God the Son and God the Holy Spirit. In other words, the Shorter Catechism definition of God should be viewed as a description of the Triune God – Father, Son, and Holy Spirit – and not just a description of God the Father.