The Rational Future Institute



Analogical Reasoning

A technique for exposing one's biases that relies on making analogies. Irrational bias is often caused by emotional attachments to conclusions or to peculiarities about the case being considered. In analogical reasoning, the reasoner imagines a comparable situation in which the reasoner's emotional attachments are reversed.

Availability Bias

The human mind tends to take the most memorable events as statistically representative. This creates a bias because usually the most memorable events are not the common and ordinary events. For example, successful airplane flights are not typically reported by the news, and not as easily recalled as airplane accidents. Consequently, many people think airplane flights are much less safe than they really are.


A foundational assumption. An axiom is a proposition that is taken to be a starting fact from which other facts might be inferred.


Bayes' Theorem

Bayes' Theorem is a rule that tells us how to update confidence in a theory given new evidence. (Wikipedia)

Bayesian Reasoning

Bayesian reasoning is a form of inductive reasoning based on Bayes theorem.


Belief is confidence in the truth or falsity of a proposition.


A bias is a tendency to reach a particular kind of conclusion.


Cognitive Bias

Cognitive bias usually denotes a bias that draws a thinker away from ideal reasoning.

Cognitive Dissonance

The theory that minds experience strong discomfort when trying to hold two conflicting beliefs at once. Cognitive dissonance is important in the study of cognitive biases because people will often discard facts in favor of beliefs about self-image.

Conditional Probability

Denoted P(A|B), conditional probability is the probability of A given B. For example, the conditional probability of rolling a 6 given a random roll of a fair, 6-sided die is 1 in 6 (16.67%).

Critical Thinking

Critical thinking refers to a set of practices that help people correct their automatic beliefs in order to get back to an ideal rationality.



A principle for inferring specific facts from more general facts.

Deductive Logic

A detailed set of rules or allowed moves for inferring specific facts from more general facts.



Pertaining to value judgments, especially where a decision affects many people.


Conscious awareness of mental or sensory phenomena.



A fact is a proposition that is actually true.





An ideology is a strategy based on values. Sometimes, the ideology is valued for its own sake, not because it will result in any particular material outcome.


The principle of inference that takes specific facts or data and infers general facts or rules. Induction provides a probability that a theory is correct, but does not give certainty. For example, using induction, one can take the experience of many encounters with another person and infer their general personality.

Inductive Logic

Inductive logic consists of specific rules for calculating the relative probability that a theory is correct given accumulated evidence.


The process of gaining new facts from existing ones.


An intuition is an automatic or subconsciously acquired belief that has not been consciously justified according to the principles of rational inference. Intuitions are not necessarily irrational. It would be better to call them pre-rational beliefs.

Irrational Belief

An irrational belief is a belief that is mistakenly believed to have resulted from the rules of rational inference. The mistake could be due to a lack of understanding of rational inference, or may be due to a mistake in applying the principles of rational inference to the evidence.




For our purposes, knowledge is defined as rationally justified belief.


Law of non-contradiction

See Principle of non-contradiction


A logic is a set of formal rules that implements the principles of rational inference. There are many formal logics, and each logic declares what rules must be followed at all times, and therefore, determines what outcomes are contradictory.



Pertaining to action and decision-making. Decision-making requires a sense of value.





A statement that is taken to be true in order to infer a conclusion. The premise may be assumed true hypothetically or may be taken as true because it was rationally inferred to be true.

Pre-rational Belief

A pre-rational belief is a guess or intuition that  has yet to be justified by the principles of rational inference. A pre-rational belief might be correct, but it isn't necessarily rational.

Principle of Indifference

The principle that, when all we know are the number of distinct outcomes, we should assign equal probability to each outcome.

Principle of non-contradiction

The principle of non-contradiction is a rule for reaching new facts from existing facts. The rule says that contradictions are to be excluded as candidates for new facts.

Prior Probability

Bayesian reasoning describes how to update confidence in the theory given new evidence. A prior probability represents our confidence in a theory before the new evidence is factored in.

When no evidence has been accumulated, the prior probability is typically spread out across all possible theories (uniform priors). For example, if you are playing poker with 3 other players of comparable ability, then the prior probability that you will win the next hand is 1 in 4. 25% of the probability is allocated to each player. The probability that you will win is shifted as cards are exposed to you, and as you infer the strengths of poker hands through the betting process.


A statement that is either true or false.



Rational Inference

A inference that follows deductive or inductive logic.


A rationalization is a valid but unsound argument that offered in support of an intuition.


Rationality The principle of non-contradiction is a rule for reaching new facts from existing facts. The rule says that contradictions are to be excluded as candidates for new facts.



The facts of your conscious awareness and your conscious memory constitute self-knowledge. Your awareness and memory may be misleading, but you can't be mistaken about what appears to you. For example, if you see a dragon in your back yard, then you believe you see a dragon in your back yard, even if the dragon is an optical illusion or hallucination. This makes appearances and observations a form of self-justified knowledge of appearance and observations.


An argument is sound if it is valid (contains no logical errors) and if its premises are considered likely to be true.



A theory is a set of axioms that explains appearances and observations. Theories are statements of conditional probability, stating the probability of making certain observations if the theory is true. These conditional probabilities are inputs into Bayes theorem which enables us to assess the probability of the theory being true given the evidence.




An argument is valid if it follows the rules of inference. The conclusion of a valid argument is correct as long as the premises are assumed to be true. A valid argument, may not be sound, however.


Values are convictions, biases, or tastes that provide a preference for certain states of affairs. Values are necessary for making choices between actions that result in different states of affairs.






Copyright 2011 Rational Future Institute NFP