Commonly Accepted Requirements For Truth


One of the base assumptions used for hunting lies amongst truth is that all true things must be compatible with all other true things (that a thing cannot have a property and also the negation of the same property is a special case of this). Consistency is the vision that drives all rational attempts to understand the world, and its tool is the paradox.


There are some operations that are believed to yield a new truth when fed truth. Some truths are considered true simply because they logically follow from other things considered true. In these cases, the logical laws themselves (modus ponens, etc.) either are axioms or rely on other axioms. Just because these laws are considered tautological to those who accept them doesn’t mean that they don’t raise difficult semantic questions on further thought.

Simple (Occams Razor)

The model which requires fewest assumptions is assumed to be better than the others. Maximal simplicity. This is a very elegant principle, but of course a massive assumption. When it comes to some issues, it’s not a very helpful principle, for example, I can assume that I create everything that is every time I breathe out and I have a model of the universe which contains very few assumptions. Deciding the correct granularity of assumptions is not something that can be done without recourse to other assumptions. Occams Razor is a good basis for faith, but there is no law that says the universe must be simple, so it can’t be considered a means of establishing truth. For example, you’re perfectly justified in believing that your TV remote works by firing balls of invisible waves that can travel through complete emptiness if you think that contains fewer assumptions than a telepathic pixie helping you out, but if you investigate and discover a telepathic pixie actually is behind it, you can’t just cry Occams Razor and fail to accept it.

Non subjectivity

Truth should be the same for all observers (or so I’ve been told). This is an idealised requirement, some people take the fact that no two measurements by two different people are exactly the same to a philosophical extreme. There has also been a trend in more modern science to promote the importance of the observer, to the extent that this requirement is not as key as it used to be. A variant would be that all truth should be investigatable by everyone. Otherwise it’s not fair.


Again, this is a weak requirement, more to do with investigation than truth. Really it dictates that there is no point in investigating something that cannot be established. Assigning a truth value to something that that cannot be established is a matter for faith, not rationality (except for the axioms of course). At this stage, the nature of proof (or what it means to establish something) becomes a problem. People have different standards of proof. For example, the Intuitionists deny themselves the ability to use some mathematical formulae because they insist on a smaller set of assumptions than most mathematicians. What an intuitionist considers proof is stricter than what a normal mathematician does. Many people believe that nothing in the real world can be considered established since our entire interaction with it consists only of inductive arguments, which other experience from the real world tells us are not infallible.

Predictive Power

Arguably a better way of evaluating different models than working out which are falsifiable is to look at the predictions that they make that conflict with previous or competing models and see which is more successful at predicting things. To count, these things should ideally not have been thought of before the model predicted it, and then they have to be confirmed by observation.

Relationship to the perceived world

Truth should be consistent with observation. No one denies that perceptions can be false but truth is almost always assumed to have some relationship to what is observed. Although some talk of truth in terms of an imagined world, exactly what value that ‘Truth’ would have except in such a dream world is hard to say. By an outside chance the dream world, at the mercy of human pyschology, could share some facets with our perceived world. It’s always possible to imagine a ‘disturbed’ pyschology where certain logical truths don’t hold. If you accept that, then you’d probably have to accept that the only difference between the ‘disturbed’ pyschology and the ‘normal’ psychology is not truth or falsity, but success and utility.

Have I missed anything? Am I wrong? Leave a comment

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