Arguments based on observation - Cosmological arguments

Change and the First Way

Cosmological arguments ask why dependent reality exists or operates at all. Aquinas' First Way begins with observed motion, meaning change more broadly than movement from one place to another. Heating and growing also count. His reasoning in Summa Theologiae I.2.3 uses potentiality and actuality.

A cold object is potentially hot; something already actual in the relevant respect, such as a fire, makes it actually hot. What is merely potential cannot actualise itself in that same respect. A thing can change another and itself undergo other changes, but it cannot be both merely potential and already actual in the same respect at the same time.

The reconstruction is: change occurs; change involves actualisation of a potential; this requires an actual source; a chain of sources whose activity is derivative cannot explain itself without a non-derivative source; therefore there is an unmoved mover. Aquinas identifies this as God.

The regress objection is often misunderstood. The explanatory problem concerns an ordered dependence of movers, rather than simply how many years the universe has existed. A stick moves a stone only because it is being moved by a hand: the stick's causal role is derivative. An indefinitely long collection of dependent instruments would not, Aquinas argues, supply the source of their activity. A temporal sequence in which one event follows another is not automatically the same kind of dependence.

A critic can challenge whether every change needs this account of actualisation, or whether dependent causes require a source outside their series. Merely pointing to a self-moving animal does not settle the issue, because its changing parts may actualise one another in different respects. A fair objection addresses the metaphysical explanation itself.

Causation and the Second Way

Aquinas' Second Way begins with an order of efficient causes. An efficient cause is a source of an effect or change, rather than the effect's purpose. Nothing can be the efficient cause of itself, because it would need to exist in order to bring itself into existence.

In an ordered series, intermediate causes depend on a prior cause for their causal activity. Aquinas argues that removing the first cause removes the dependent effects; an endless series without a first would therefore not explain the effects that exist. He concludes that there must be an uncaused first efficient cause, called God.

The argument does not simply claim that everything has a cause and then make an exception for God. Its disputed claim is that the observed order of dependent efficient causes requires a non-dependent cause. If the premise were literally everything has a cause, an uncaused God would indeed contradict it. Accurate reconstruction avoids criticising that weaker substitute.

There is still a serious question: why does explanation have to end in a transcendent cause rather than a fundamental physical reality, or an infinite order? A defender says a fundamental dependent cause would still require explanation. A critic asks how we know physical reality as a whole is dependent in the same way as particular processes. The claim of a first cause also does not yet establish personality, goodness or the full attributes of the God Aquinas discusses elsewhere.

The First and Second Ways overlap but are distinct. The First analyses change through actualisation. The Second analyses dependence in efficient causation. Naming both first-cause arguments without explaining that distinction loses their reasoning.

Contingency and the Third Way

Aquinas' Third Way distinguishes things that can exist or fail to exist from what is necessary. A contingent being does not have to exist: familiar organisms come into being and perish. A necessary being cannot fail to exist, although Aquinas also distinguishes beings whose necessity depends on another from one necessary through itself.

The text first argues that if everything were able not to exist, at some time nothing would have existed. If nothing existed, nothing could begin to exist, because something already existing is needed to generate it. Since things exist now, he concludes that not all beings are contingent. He then rejects an infinite regress of beings whose necessity is received from another, arriving at a being necessary through itself and the source of others' necessity.

The first stage needs careful evaluation. From each being sometimes not existing, it does not obviously follow that all beings are absent together. A relay team can have each runner resting at some time while someone is always running. That is an analogy exposing the inference's form, not a proof that an infinite contingent universe exists. Aquinas' reasoning needs assumptions about the series and possible non-existence that the simple wording does not fully establish.

An alternative contingency argument asks why the whole dependent order exists, without claiming there was literally a time when nothing existed. This can be a stronger development, but it should be identified as a reconstruction or later argument rather than silently substituted for every step of Aquinas' Third Way.

The final distinction also matters: necessary through itself is not the same as simply long-lasting. An eternal object could still depend on a cause for its existence. Aquinas seeks an ultimate ground, not merely the oldest surviving object.

Regress and the whole universe

Two objections must be kept separate: whether an infinite regress explains dependence, and whether a property of parts belongs to the whole. Rejecting every infinite series simply because it is infinite is not enough. A defender of Aquinas instead argues that an infinite series of derivative causes remains derivative: increasing its length does not change its explanatory type.

The fallacy of composition occurs when a property is transferred from members to a collection without justification. Every tile can be small while a mosaic is large. Likewise, each event having a cause does not automatically establish that the universe, as a collection, has a cause beyond it. The criticism is strongest against a bare parts-to-whole inference.

A defender can reply that dependence differs from size. A collection made entirely of things whose existence is borrowed might still need a ground of that dependence. That is an additional argument about explanation; the answer cannot simply repeat that each part is caused. A critic may regard the whole as a brute fact, or hold that explanation of its members is enough.

These objections do not identically affect all three Ways. The First and Second focus on ordered dependence; the Third contains both a debated temporal inference and a regress of dependent necessity. Precision about which premise is challenged allows a meaningful reply. Calling every difficult step a logical fallacy without reconstructing it is not analysis.

From ultimate ground to creator

Aquinas identifies the ultimate source as God, but an argument's immediate conclusion must be distinguished from all the attributes later attributed to it. An unmoved mover, uncaused cause or independently necessary being is not yet explicitly shown to be a loving personal creator who freely creates from nothing.

Transcendent means beyond or independent of the created order; immanent concerns presence or activity within it. A cause outside the dependence of a system need not be somewhere physically outside a spatial boundary. Asking where God stood before space existed therefore misstates the proposal. The real question is whether the argument justifies a non-physical independent ground at all.

A defender can say that a dependent world ultimately needs a being whose existence is not borrowed; further arguments may establish unity, intelligence or goodness. A critic can accept a fundamental reality while rejecting its identification with the God of religion. Both responses recognise the gap rather than pretending it is either self-evident or fatal to every possible development.

A qualified judgement could therefore find the Ways persuasive as arguments that dependence raises a serious explanatory question, while denying that their short forms alone establish a full transcendent creator. Alternatively, a defender could maintain that the nature of a wholly non-dependent cause rules out a merely contingent physical stopping point. That judgement needs reasons linking independence to the proposed attributes. Hume's criticisms in the next lesson test both the causal inference and the temptation to infer more than the evidence supports.