The idea that some terms are used analogically had its roots in Aristotle, but was discussed extensively by Arabic philosophers in the heyday of Islamic philosophy (including Al Farabi (870-950), Ibn Sina (980-1037, sometimes called Avicenna) and Al Ghazali (1058-1111) and by Christian thinkers such as Aquinas' tutor, Alexander of Hales, in the early thirteenth century. Originally, the term "analogical" was related to the term "ambiguous", stressing the uncertainty over the degree of meaning that could be shared by the same word used in different senses. St Thomas Aquinas (1225-74), a Dominican, was brought up in a philosophical world that was obsessed by logic and grammar. As all aspiring academics at the University of Paris did, Aquinas commented on Aristotle'sCategories, one of the two works of Aristotle available in Latin prior to the early twelfth century. Aquinas developed the idea that terms applied to God are analogical, but tried to explain exactly what the proportion and nature of shared meaning would be when a term is applied to God and to an earthly thing. Using Aristotle's distinctions, he did not believe that terms applied to God are equivocal (essentially meaningless) but he did not believe that they should be seen univocally either, words applied to God cannot mean exactly the same as if they were applied to things in the world of experience. For Aquinas, God created the world and therefore it must tell us something about Him, but God is other, different from the world of time and space and potentiality that He caused to be.
Aquinas' Doctrine of Analogy
Language tends to imply a worldly framework. If I say that Peter acts then we can imagine what that might mean – but how can God act in the same way? God is beyond time and space, he doesn't have a body, so what can God's action really mean? For Aquinas, language can only be used analogically of God (from analogia, the Greek for proportion). Saying Mary is good and God is good shares some meaning, a proportion of the meaning, but not all the meaning. Aquinas uses a truly medieval example to explain. A good bull has a sleek coat, big muscles and a strong interest in cows; a good God would scarcely have these attributes! Nevertheless a good bull also produces good things (healthy urine and manure, high-quality semen and prize-winning calves) and does what good bulls are supposed to do, conforms to the ideal. In this we can see the proportion of meaning that could be shared between a good bull and a good God. God could also produce good things and fully fulfil his divine nature, not falling short in any respect. God being good in that he produces good things is known as analogy of attribution; God being God in that he perfectly fulfils His nature is known as analogy of proportion. Altogether, this is known as Aquinas' Doctrine of Analogy.
In summary, some scholars see that language can be used literally or univocally of God. These include St Anselm and Duns Scotus for examples. Other scholars see that language can never be used to describe God. Words are bound to space and time and God is beyond both; words applied to things and to God would share no meaning and would be equivocal (like bat as in cricket and bat as in flying rodent). These include Maimonaides. Aquinas takes a middle way, arguing that a proportion of meaning is shared through his doctrine of analogy.
Scotus – one meaning, differing degrees
John Duns Scotus (1265-1308) came from Scotland before studying at Oxford, Cambridge and Paris. He was a Franciscan and so balanced his philosophical genius and scholarly positions with a sincere belief that Christianity was about ministering to the poor and taking the Gospel message literally. Scotus applied his mind to defending the possibility of using language univocally, so that saying "God is good" or "Jesus is the Word of God" can be understood unequivocally. Like St Anselm (1033-1109) he held that "[t]he difference between God and creatures, at least with regard to God's possession of the pure perfections, is ultimately one of degree" Whereas earthly things are limited by their physical existence, God is infinite and has no limitations. When we say God is good, the concept of goodness is the same as when we say "Peter is good", but to a much greater degree.
Aquinas compared to Scotus
This contrasts with the thinking of Aquinas. Aquinas suggests that God is wholly simple and thus other, not a thing. Language is tied to things with earthly limits and only a proportion of the meaning can be shared between a word applied to God and the same word applied to a thing. While Scotus' concept of God as infinite is similar to Aquinas wholly simple God on one level, on another it is very different. As Professor Thomas Williams of the University of South Florida writes, "For Scotus infinity is not only what's ontologically central about God, it's the key component of our best available concept of God and a guarantor of the success of theological language. That is, our best ontology, far from fighting with our theological semantics, both supports and is supported by our theological semantics." In other words, if we believe that we can define and understand God at all, then this guarantees that the reason and language with which we define Him is a reliable means of defining and understanding Him. Denying the univocity of language would, for Scotus, deny the possibility of meaningful philosophy and religion.
Scotus, like Aquinas, assumed an Aristotelian worldview. All things are caused and (at least for the Christian philosopher) this suggests that all things must have either been kept in being or initially have been brought into being by an "uncaused causer", which is what we call God. If God is the original cause of all things then it is reasonable to expect that the cause and the effect share characteristics. Just as you share characteristics with your parents and someone could understand something about them by knowing you, and just as your Technology project might reveal something about you, creation might reasonably reveal something about God. Further, for Scotus, the concept of "being" (Latinens) cannot be seen to be analogical. For something to exist must mean the same in any situation and in this at least we can have direct understanding of what God is, being itself. Where Scotus and Aquinas were influenced by Aristotelian philosophy, René Descartes (1596-1650) had a more Platonic view of concepts or ideas.