Alexander Pruss's Blog

• Does everything in time change? 2026-01-29
  Over the last two days, I’ve been thinking critically about Aquinas’ First Way. Central to my thinking, and especially yesterday’s post, was the idea that you could have an unmoved mover who is in time but isn’t pure act and who isn’t God. Such an unmoved mover constantly and unchangingly exercises—perhaps mentally—one and the same […]
• Gale's criticism of Stump and Kretzmann's ET-simultaneity 2026-01-29
  Stump and Kretzmann give three main concepts of simultaneity in their famous paper: T-simultaneity between items in time E-simultaneity between items in eternity ET-simultaneity between items in time and items in eternity. Stump and Kretzmann observe that ET-simultaneity is not reflexive: a temporal item is not ET-simultaneous with a temporal item and an eternal item […]
• Does it follow from van Inwagen's answer to the Special Composition Question that all complex things are alive? 2026-01-28
  The view that all objects are either living or simple appears to be a consequence of van Inwagen’s answer to the special composition question, namely that a proper plurality only composes a whole when the parts have a life together, where a proper plurality is a plurality of two or more things. But this does […]
• Proper parts and dependence 2026-01-28
  Consider this initially plausible thesis: If x has a proper part, and all of x’s proper parts depend on y, then x depends on y. Add: An effect depends on its cause. Nothing depends on itself. We conclude: Nothing that has proper parts is a cause of all of them. This has a nice theological […]
• How do we get to an unmoved mover? 2026-01-28
  I just realized that there is a difficulty in Aquinas’ First Way that I think hasn’t been noted, which builds on the difficulty noted yesterday. Put the First Way in the following simpleminded way, which I think captures the central ideas: Causes of change are either passers-on of change or originators of change. It can’t […]
• An easily patched hole in the First Way 2026-01-27
  In his First Way, Aquinas argues that as we trace back the sequence of movers from effect to cause, we get to a first unmoved mover, and this is God. But need the unmoved mover thus reached in the sequence of movers be God? Imagine this scenario. God creates some material beings, as well as […]
• Explanatory principlism 2026-01-27
  There are three views about ultimate explanations of reality: Nihilism: There is no ultimate explanation of reality. Onticism: The ultimate explanation of reality involves one or more beings. Principlism: The ultimate explanation of reality involves principles rather than beings. Nihilism is the standard view among atheists. Onticism is the standard view among theists. The main […]
• Punishment and presentism 2026-01-20
  This seems a bit plausible: It is unjust to punish someone for a feature that is not intrinsic to them. If presentism is true, then having done A is not an intrinsic feature of the agent. Thus, if presentism is true, then punishment for past actions is always unjust. The presentist may well question (2), […]
• Old Polish Almond Torte 2026-01-08
  In my family, when someone (including me) has a birthday, they choose a type of cake, and then I bake it, often with the help of one or more kids. A family favorite is the old Polish Chocolate Almond Torte. This is a gluten-free cake, made of almond meal, with leavening provided by a full […]
• Fine moral distinctions 2026-01-07
  I find myself sometimes troubled by narrow moral distinctions in the Christian, and sometimes more specifically Catholic, tradition. Lying is wrong, but deception—perhaps including verbal deception—is not. Intentionally killing the innocent is wrong, but redirecting trolleys onto innocent people can be acceptable. Salpingostomy is wrong as a treatment of ectopic pregnancy, but salpinectomy is right. […]
• Permissivism about lying 2025-12-29
  I am an absolutist about lying: I think it’s always wrong to lie. But even if I were a permissivist about lying, I would think that there are certain subject matters about which it is always wrong to lie, no matter the costs and benefits. It is completely clear to me, for instance, that it […]
• Dishes of food 2025-12-26
  Let’s say I am eating a dish, say a soup, a salad or a sandwich. At some point there is half-eaten dish, and finally all that’s left are some odds and ends. When did the dish perish? One option is that the dish perished when the elements distinctive of the type of dish have been […]
• God and growing block 2025-12-15
  On the growing block theory of time, if God is in time, God grows. God doesn’t grow. So, God is not time or the growing block theory is not true.
• Divine timelessness 2025-12-15
  This is probably the simplest argument for the timelessness of God, and somehow I’ve missed out on it in the past: God does not change. Creation has a finite age. There is nothing outside of creation besides God. So, change has a finite age. (1–3) There is no time without change. So, time has a […]
• Semi-statistical views of health 2025-12-12
  On a purely statistical views of health, the health of a bodily system is its functioning near the average or median. This leads to the absurd conclusions in Kurt Vonnegut’s “Harrison Bergeron”: we should push those who are above average closer to the average. A better view is Bourse’s semi-statistical view on which non-statistical facts […]
• Using general purpose LLMs to help with set theory questions 2025-12-11
  Are general purpose LLMs useful to figuring things out in set theory? Here is a story about two experiences I recently had. Don’t worry about the mathematical details. Last week I wanted to know whether one can prove a certain strengthened version of Cantor’s Theorem without using the Axiom of Choice. I asked Gemini. The […]
• Plural quantification and the continuum hypothesis 2025-12-10
  Some people, including myself, are concerned that plural quantification may be quantification over sets in logical clothing rather than a purely logical tool or a free lunch. Here is a somewhat involved argument in this direction. The argument has analogues for mereological universalism and second-order quantification (and is indeed a variant of known arguments in […]
• Maybe we can create spacetime 2025-12-09
  Suppose a substantivalist view of spacetime on which points of spacetime really exist. Suppose I had taken a different path to my office today. Then the curvature of spacetime would have been slightly different according to General Relativity. Question: Would spacetime have had the same points, but with different metric relations, or would spacetime have […]
• Time without anything changing 2025-12-08
  Consider this valid argument: Something that exists only for an instant cannot undergo real change. Something timeless cannot undergo real change. There can be no change without something undergoing real change. There is a possible world where there is time but all entities are either timeless or momentary. So it is possible to have time […]
• The last thought 2025-12-08
  Entertain this thought: There is a unique last thought that anyone ever thinks and it’s not true. Or, more briefly: The last thought is not true. There are, of course, possible worlds where there is no last thought, because (temporal) thoughts go on forever, and worlds where there is a tie for last thought, and […]