There are numerous examples of ontological reduction, or elimination in the case of moral anti realism, the denial of the existence of a philosophical God (Russell's brute fact) and physicalism/materialism. A lot of these theories are generally accepted as being the most accurate today.

However, a lot of the power of these arguments comes from the fact that they are attempting to prove the existence of very little. If they had to prove the existence of something, then they would have far less power. As I will demonstrate, arguing for a lack of existence is far easier than arguing for an existence, but this shouldn't affect an argument's overall power.

Consider this thought experiment. Conceive of a sentient, thinking entity that has no experience of the world and trying to persuade them that trees exist. This would likely be impossible. Now conceive of trying to persuade them that trees do not exist. Whilst trees do exist, it is easier to persuade the entity that they do not. So, facility with which we can prove something should not equate to whether one theory is better than another.

Take the case of emotivism. It is very easy to persuade us the moral properties do not exist, as we have little intuitive means of experiencing their existence. This shouldn't mean however, that moral anti-realist theories succeed over realist theories, simply because it is easier to argue for.

It is because of this that I believe that the reason for the general acceptance of these theories is that they are easy to believe and argue for, not that they are necessarily correct. Therefore, I ask the question, shouldn't these ontologically reductive theories be re-evaluated?

  • Unlike anti-realism and atheism, physicalism is not trying to prove a negative, it is a pretty controversial positive thesis that everything observed is governed by physical laws. Physicalists argue for existence of matter with properties that would cover all that, which is not a little. It also goes against many common intuitions and so is not easy to believe either. And generally, we have no means of establishing that something is correct other than arguing for it based on available evidence, so you'll need more than "it could be" hypotheticals for a successful re-evaluation proposal.
    – Conifold
    Oct 10, 2023 at 20:46
  • Indeed ontologically reductive physicalistic theories including noncognitive moral emotivism or error theory are very popular and powerful, many philosophers and scientists are working hard to try to make it even more powerful such as to solve 'hard problem of consciousness', the origin of life, the unification of QM and GR, quantum constructors, etc. Regarding your "It is because of this that I believe that the reason for the general acceptance of these theories is that they are easy to believe and argue for", why 'easy to belief' is a concern? Per Occam's razor it should be preferred... Oct 10, 2023 at 23:58
  • Plenty of people believe that things exist which they can't prove. It is not that non-existence is easier to believe... But it is much more likely.
    – Scott Rowe
    Oct 11, 2023 at 10:58
  • From many Christian perspectives, faith is neither easy nor difficult per se: either it is simply impossible for us to believe of our own accord but either God grants the (ir)resistible grace-to-believe or not, and that is that. Or perhaps everyone automatically "believes in the existence of God" (so that the demons tremble, etc.) on some deep, subconscious enough level, whatever they say out loud. I used to be in those kinds of camps, am no longer, but I would still wonder about assigning a level-of-difficulty to such faith... Oct 11, 2023 at 12:55

2 Answers 2


The answer is Bayesian inference. There are prior probabilities and posterior probabilities. Each possible theory begins with some prior probability, different for different theories. After seeing some evidence compatible with a theory, we may revise the posterior probability upwards from the prior probability. If there is enough evidence, the posterior probability becomes high enough to say that the theory is credible or that we believe it.

Simpler theories get higher prior probabilities. This is Occam's razor. It means that the simpler a theory is, the less evidence is required to increase the posterior probability enough to say that we believe it.

One way to think about Occam's razor is in terms of conjunctions. If A and B are two conditions that a theory says hold, P(A and B) <= P(A). That's a law of probability; adding a condition to the theory usually makes the theory less likely, and can never make it more likely. We can also say P(A and B and C and D) <= P(A and B and C) <= P(A and B) <= P(A), and so on. The more conditions we add to the conjunction, the less likely the theory becomes. Usually it becomes exponentially less likely with each new condition.


Tree word is lexicographical. For someone who has no experience, must learn the language English or Chinese or Hindi before you can debate the existence of trees. Words are learned through experience of a picture , sound , taste , touch or smell or pain or pleasure or attractiveness or unattractiveness etc. To teach someone there is a tree you must teach him by any of the above means. Similarly to teach that there are no trees you must express what is meant by trees? Both ways you must convey the meaning before it can be denied or accepted.

Morality is a tool to develop civilised societies. Again you must demonstrate what is meant by morality before accepting it or denying it.

Ontological reductionism must be re-evaluated because we don’t learn words that way. We don’t teach parts to learn the whole neither we teach whole as if they are without parts. In fact some hint is sufficient to express the truth. For example a faint smell can produce saliva in your mouth and bring back the memory of food because you are so familiar with the food.You don’t see the whole , only one aspect of it still it brings back the picture of the whole. Similarly whole food can be understood as made up of parts of smell , taste , colors , texture etc.

  • I like your point that you have to teach someone a concept before showing that it doesn't exist. But then, it seems like a real waste of time to do that. We should stick to stuff we know exists.
    – Scott Rowe
    Oct 11, 2023 at 11:01
  • Perhaps a better example than my tree one would be attempting to convince a blind person that colour exists, in a room of five people, with again no prior experience of the world. It would be far easier to do the inverse.
    – sket
    Nov 22, 2023 at 23:19

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