moral reasoning

argument

the application of principles of reasoning to prove, or provide support for, one statement on the basis of other statements

deduction

a logical argument in which a conclusion is derived from one or more premises by strict logical rules. a valid deduction from true premises must yield a true conclusion.

premise

the starting point of an argument, from which a conclusion is deducted by means of logical rules

conclusion

the end point of argument, which if the argument is logically valid, will be deducted from one or more premises by means of logical rules

logical validity

an argument in which, if the premises are true, the conclusion must also be true, has logical validity. in a logically valid argument, negation of the conclusion contradicts the premises; this is how the logical validity of an argument can be tested

contradiction

two (or more) statements that, purely for reasons of logic, cannot all be true

logical necessity

if a conclusion is validly deduced from one or more premises, then the conclusion follows by logical necessity

soundness

the quality of a valid argument derived from true premises. if the premises are not true, an argument is unsound even if it is logically valid

logical form

an argument in ordinary speech can often be reconstructed as a step-by-step logical argument, thereby revealing its logical form

equivocation

using a word in more than one sense in an argument. generally to do so renders the argument invalid

begging the question (circular argument)

an argument that uses what is intended to be the conclusion as a premise in the argument. because it assumes what it is attempting to prove, it does not prove anything.

analogy

making a comparison between two areas of knowledge or investigation in the hope that what is known about one area will bring insight into the other

induction

providing support for a general hypothesis by observing repeated instances of it. for example, the hypothesis that all swans are white can be supported through induction by finding many examples of white swans. however, induction is never proof.

refute

to conclusively demonstrate that a claim or hypothesis is false. in common use, the term is often used to mean deny or rebut, but strictly refure has much stronger meaning

inference to best explanation

arguing for a theory on the basis that it provides the best explanation of some observed phenomenon. for example, it is generally believed that the best explanation of the correlation between smoking and lung cancer is that smoking causes lung cancer, even though other possible explanations are also available

abduction

another term for inference to the best explanation

thought experiment

a fictional scenario created to illustrate a theory or to test it against our intuitions

utilitarianism

the moral theory that the right thing to do in any circumstance is to bring about the greatest total balance of happiness over unhappiness

moral intuition

a reaction to a situation, whether real or a thought experiment that expresses the opinion that what has been described is morally acceptable or unacceptable

counterexample

an example used to show the falsity of a claim or hypothesis. for instance, the observation of a green swan is a counterexample to the hypothesis that all swans are white.

universalization

considering the moral appropriateness of an action by imagining a world in which everyone did what you propose to do

fact/value distinction

the claim that there is a sharp distinction between issues of fact and issues of values, accompanied by the claim that it is a logical fallacy to try to derive value conclusions purely from factual premises

slippery slope

the argument that although something seems relatively innocent or harmless, it is likely in some way to lead to something much more problematic

doctrine of double effect

the argument that what matters from the point of view of moral responsibility are the effects that you intend, even if you can forsee that your actions are very likely to have harmful side-effects. the concept is often used in discussion of the ethics of war.

framing

the recognition that a person’s intuitions about problems, including moral problems, can be heavily dependent on how the problem is described; logically equivalent descriptions of the same problem can typically elicit different answers from the same person

confirmation bias

the tendency to look for evidence that supports a view you already disposed to believe and to ignore or discount any contrary evidence