New and Old Ways of Reasoning to God
By explanation I mean some principle that removes mystery.
Often enough, explanations are causes. The fire caused the pot to be hot. Thus, the fire explains the hotness of the pot.
But not all explanations are causes. For example, we know why there are no square circles, not by pointing to any cause or lack thereof, but by pointing out the contradictory structure of what’s asserted. Because contradictions are impossible and because square-circles are contradictory structures, this explains why there are no square-circles.
So while all causes are explanations, not all explanations are causes. Moreover, there are philosophers who believe certain things may be self-explanatory, either concerning their existence or activity or both. In fact, that is often what theists say about the existence of God – namely, there is something about God’s nature that is like the opposite of a square-circle: rather than it being impossible for God to exist, it is impossible for God not to exist. God is a necessary being, explained in his existence by having a special nature, one radically unlike anything in physical reality.
We can come to explanations in several ways.
First, we may develop a hypothesis and then see if that hypothesis accurately predicts some data or phenomena and does so better than rival hypotheses, preferably with fewer commitments. If so, we feel that hypothesis might be a good explanation of that data — i.e., the true explanation.
Suppose my driveway is wet. What explains this? Perhaps my sprinkler turned on. This predicts the data I see – not just the wetness of my driveway, but the lack of wetness of my neighbor’s driveway, which I would expect to see if, say, it rained. The data supports my hypothesis well, and so I think the sprinkler is the probable cause, explanation, or reason why my driveway is wet. Here, the inference is probabilistic.
Alternatively, we may move from effect back to necessary condition. I notice my driveway is wet. What can infer from this, not probabilistically, but certainly? Almost trivially, that there must be something with a wetness producing power. Of course, this leaves my understanding of the cause or explanation vague; I haven’t articulated just what that something is. Nevertheless, I take it that something of a wetness producing power is a necessary condition for my driveway being wet, however uninformative that may be. Still, it is not totally uninformative, for I’ve still been able to affirm that there exists, or did exist, something with a wetness producing power. And I might not have known this prior to seeing my wet driveway.
The illustrations above contrasts two common methods for thinking about God as the ultimate explanation of things, the new way (inference to the best explanation) and the old way (metaphysical demonstration), respectively.
To illustrate, some philosophers begin by forming a worldview hypothesis that features God as the fundamental entity, then argue that this hypothesis best predicts or explains the phenomena of our experience. For such reasons, the “God hypothesis”, as it were, is the one most probably true. This method consists in assembling data requiring explanation then asking whether that data is more expected given the God hypothesis versus some rival hypothesis (naturalism, say). Richard Swinburne is a champion of this approach.
Other philosophers – and this approach is more traditional – begin with effects and reason back to necessary conditions, such if those necessary conditions did not attain then neither would the effect. Nothing with a wetness producing power, then no wet driveway.
Concerning natural theology, traditional philosophers have said the same thing about certain very general aspects of experience and the existence of God. For example, that the necessary condition for any changing thing is at least one unchanging thing, that the necessary condition for any contingent thing is at least one non-contingent (or necessary thing), that the necessary condition for any composite thing is at least one non-composite (or simple thing), and so on. I am not defending these arguments now, only highlighting the reasoning at play. Read Aquinas for specifics.
Nevertheless, when it comes to moving from effect to cause, the difference concerning the existence of God and the existence of something with a wetness producing power, is this. I cannot infer much else about what that something of a wet-ness producing power is — is it a sprinkler, a heavily drooling dog, or… ? However, philosophers argue one can go further in figuring out that an unchanging or necessary or incomposite being is God as understood by classical theists. For example, by arguing that a necessary thing must be a being of pure actuality, which itself must be utterly simple, omnipotent, necessary, and so forth.
The above is merely suggestive (not dispositive), highlighting that effect-to-cause reasoning about God may be more informative than one initially suspects, at least if they are willing to engage a deeper conceptual analysis of what a necessary (or unchanging or incomposite) being is.
[1] For a further articulation and defense of Aquinas’s argument specifically, see Gaven Kerr, Aquinas’s Way to God: Proof in De Ente et Essentia (Oxford, UK: Oxford University Press, 2015) 18-30.