# Self Evident Truths

There are a number of ways that something can be self-evident. In ordinary language, we say that something obvious is self-evident. Philosophically, however, further distinctions must be made. In modern philosophy, something is self-evident when understanding what it means immediately results in knowing that it is true. In Aristotelian philosophy, another meaning of self-evident was used. There are four different ways of understanding self evidence – logical, indubitable, undeniable and impractical.

Something may be self-evident to one person, but not to another person. For example, I know that 2468+5589=8057. But I figured that our using a calculator. Some individuals are so skilled at math that they know the answer simply by understanding the question. But I understand the question as well. So the difference is not one of understanding, but one of degree of understanding. The math expert simply understands implications that I require a calculator to do.

Something may also be self-evident in a number of ways. First, it may be logically self-evident. Denying the statement causes a logical error. So if the box is blue and red is not blue then the box must not be blue. The last statement is self-evident given the previous statements. Second, something may be indubitable. That is, it cannot be doubted. When I see a computer in front of me, then the statement I see a computer in front of me is self evident. Such a thing cannot be doubted. Third, something may be undeniable. Attempting to deny the statement meaningfully will result in affirming it. A good example of this is the law of non-contradiction. I might claim that some contradictions are true, but my statement assumes that its logical opposite – no contradictions are true – is false. But the assumption is simply a restatement of the law of non-contradiction! Therefore, such a law cannot be denied. Fourth, something may be practically self-evident. This may be read in two ways. First, the general activities of life confirm the statement and deny its opposite. For example, it is self-evident that we need food to live. Second, attempting to disprove the statement will prove it instead. For example, attempting to prove that there is no such thing as goodness will result in an appeal to the good life or to good reason.

All of these various kinds of self-evidence are not equal. But they are all things that are the most certain to us. So there are a number of objections to the use of self-evidence. First, how could a conflict over whether or not something is self-evident be resolved? Second, couldn’t the world be made in such a way that self-evident truths are simply wrong? Third, how do we determine whether or not something is really self-evident or not? Fourth, are there a sufficient number of self-evident truths to build a philosophy on? I think that these are the central concerns of philosophers who deal with self-evident truths. (I am excluding for moment those who simply deny that there are such truths.)

## Published by

### Matthew

I have obtained an MA in philosophy from Western Michigan University. Over the years, I have been interested in philosophy, religion and politics. My philosophical interests have shifted to a focus on applying the philosophical understanding of Aristotle and Aquinas to modern problems in philosophy.

## 3 thoughts on “Self Evident Truths”

1. Susan Haines says:

‘The box is blue, red is not blue, therefore the box is not blue’ is neither logical nor self evident. Logically it would be: The box is blue, red is not blue therefore the box is not RED. A self evident truth is one that is based on no other ‘evidence’. In this case there are 2 assertions from which a conclusion has been drawn namely: ‘The box is blue’ and ‘red is not blue’. ‘The box is not red’ is deduced from the 2 previous statements. The 2 assertions are treated as self evident truths (self evident because they do not need each other, or indeed any other ‘fact’ to authentic them and ‘true’ because we accept that we all know what is meant by ‘box’, ‘blue’ and ‘red’ and they apply to the object in question) but the final assertion that ‘the box is not red’ is not in this case a self evident truth because it is authenticated (evidenced) by the information contained in the first 2 and true in the sense that it is not a contradiction of either. It is an example of (logical) deduction.
If you had a blue box we could prove that a) it is a box (using geometry) and b) it is blue (using physics and biology). Most people, however would see a blue box and agree ‘yes it’s a box’ and ‘yes it is coloured blue’ without needing any supporting evidence. In such a situation most people would accept ‘the box is blue’ and ‘red is not blue’ as self evident truths. For brevity, so too would most mathematicians and physicists! Having accepted both these assertions we will all be happy with the conclusion that the ‘box is not red’ comfortably and with no further recourse to ‘boxness’ nor ‘redness’.
FYI: To a mathematician, a self evident truth is called an axiom. Euclid managed to lay out the whole of his geometry based on just 5 axioms – which I think is pretty impressive. My love of symmetry leads me to hope (and suspect) that it may be possible to base all arguments in all languages on just 5 self evident truths or ‘premises’ but I am neither a linguist nor a philosopher. I leave it to better minds to demonstrate….
(I do wonder, though, why 5? No less and no more. Is there something significant about the number ‘5’…? Hmmm.)

1. Jack says:

Thanks for your clarification, Susan. You are a writer and a thinker. I believe some people type faster than they think and also don’t look back to edit themselves. I appreciate your willingness to see an error and correct it, intelligently, without judging or sarcasm. As for the number “5,” I believe significance is like beauty. It’s in the eye of the beholder.

2. Jakob Aggernaes says:

Maybe a better example of a ‘trivial’ self-evident truth is “sin is sin”, undeniably true, but so self-evident that it has no argumentative power whatsoever ( I met it on a forum today, which is why I searched for “self evident truth” 🙂