Rational = x x = ?

I've been defining words for myself for a while and one that I haven't defined rational yet. Anyone have a good definition for one, on a basis of utilitarianism.

  • 1
    I have one, but not on the basis of utilitarian "diction". Jan 11, 2022 at 16:39
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    If one used utilitarianism in order to derive definitions, how could that work? Think about that. But if one uses utilitarianism to derive the definition one may find that the derived definition of rational may not be related to utilitarianism at all.
    – Nikos M.
    Jan 11, 2022 at 18:11
  • @NikosM. You define words on the basis of connotation (which is essentially a hypothetical as it seems that our knowledge of connotation is based on perception) - you alter the definition of words to bring about good.
    – Swift360
    Jan 11, 2022 at 18:15
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    @anon I'd argue not, but thank you for the answer nevertheless
    – Swift360
    Jan 11, 2022 at 19:12
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    So are you looking for a definition of rational behaviour, as opposed to rational belief?
    – J.G.
    Jan 11, 2022 at 19:12

6 Answers 6


A coherent totality of communicable beliefs that are interrelated in discernible "ratios" and correspond, more or less, to causation in their material environment.


Of a belief, having accurate predictive power matching empirical data; or of an action based on such belief, maximising efficacy.


The term 'rational' is related to the term 'ratio', and implies the ability to effectively measure and balance concepts and ideas. It's a natural analogy to applying principles of geometry to crafts. A man who doesn't measure or calculate well is a sloppy craftsman, and builds (say) weak, wobbly, oddly-proportioned furniture. A man who does measure and calculate well makes sound, sturdy, well-ordered furniture. It's the same with cognitive work. Assessing premises, measuring phrases, calculating intellectual trajectories, etc.: these actions create sound, sturdy, rational arguments.


Some deep thought on "the principle of reason" can be found in Heidegger's essay The Essence of Ground in Pathmarks.

Quoting from the start and the end to give a flavour of the content.

Page 100

  1. The Problem of Ground

The "principle of reason" as a "supreme principle" seems to preclude from the very outset anything like a problem of ground. Yet is the "principle of reason" an assertion about ground as such? As a supreme principle, does it reveal at all the essence of ground? The usual, abbreviated version of the principle states: nihil est sine ratione, nothing is without reason. Transcribing it positively, this states: omne ens habet rationem, every being has a reason. The principle makes an assertion about beings, and does so with regard to something like "ground." Yet what constitutes the essence of ground is not determined in this principle. It is presupposed for this principle as a self-evident "idea." However, the "supreme" principle of reason makes use of the unclarified essence of ground in yet another way; for the specific character of principle belonging to this principle as a "grounding" principle, the character of principle belonging to this principium grande (Leibniz) can after all be delimited originarily only with regard to the essence of ground.

The "principle of reason" is thus worthy of question both in the way it is posed and in terms of the "content" it posits, if the essence of ground is indeed now able to become a problem over and above some indeterminate general "idea."

Page 132

... looking back to the point of departure of our investigation, we shall now discuss briefly whether anything, and if so, what, has been attained with regard to the problem of the "principle of reason" through our attempt at shedding light upon the "essence" of ground. The principle means: every being has its reason [ground]. The exposition we have given first of all illuminates why this is so. Because being, as understood in advance, "intrinsically" grounds things in an originary manner, every being as a being in its own way announces "grounds," whether these are specifically grasped and determined in an appropriate way or not. Because "ground" is a transcendental characteristic of the essence of being in general, the principle of reason [ground] is valid for beings. Ground, however, belongs to the essence of being because being (not beings) is given only in transcendence as a grounding that finds itself in a projecting of world.

Furthermore, it has become clear with respect to the principle of reason [ground] that the "birthplace" of this principle lies neither in the essence of proposition nor in propositional truth, but in ontological truth, i.e., in transcendence itself. Freedom is the origin of the principle of reason [ground]; for in freedom, in the unity of excess and withdrawal, the grounding of things that develops and forms itself as ontological truth is grounded.

Coming from this origin we not only understand this principle in its intrinsic possibility, but we also gain an eye for something noteworthy and hitherto unelucidated concerning the way it has been conceived, something that is, however, suppressed in the way the principle is ordinarily formulated.


A form of obligation which includes moral and extra-moral, but not aesthetic, norms: we are obliged to believe fire is hot.

  • this is fun haha
    – user57343
    Jan 13, 2022 at 13:35

Thoughts or behavior based on a set of acceptable assumptions following acceptable patterns of thought (a weak variant of being logical).

It is the opposite of irrational, with thoughts or behavior not following from acceptable assumptions, or not following acceptable patterns of thought.

If two people do not agree on assumptions, their thoughts and behaviors may appear irrational to each other. Same if they don't agree on suitable patterns of thought. However as long as they consider each other's assumptions or thoughts pattern mutually acceptable despite of differences, they would still appear rational to each other.

As such a person of science and a person of religion might consider each other as rational, or as irrational if the differences are too pronounced.

While this is subjective, a person may still perceive certain own thoughts or behavior as irrational, this is part of the human condition.

In science people strive to have assumptions backed by observations and math, and using logical patterns of thought. In philosophy, people try to have contradicting free assumptions and using logical patterns of thought backed by philosophers. Outside of science and philosophy however, people mostly strive to have a large overlap with their peers in what assumptions and patterns of thought they use, to avoid being perceived as irrational. Being "more rational" is typically regarded as a virtue for careers, whereas being too rational can be seen as a negative clashing with other demands in society, such as for compassion.

School education has the goal of grounding people in acceptable assumptions and teaching acceptable patterns of thought (among other goals), ideally still leaving enough freedom for choosing ones own path.

  • That sounds pretty close to what I'd want it to be. Thank you very much.
    – Swift360
    Jan 18, 2022 at 16:22

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