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For example, modus ponens is a rule of inference according to which all arguments of the form "(1) p, (2) if p then q, (3) therefore q" are valid, independent of what the terms p and q stand for. [13] In this sense, formal logic can be defined as the science of valid inferences. An alternative definition sees logic as the study of logical ...
An example of this is the use of the rules of inference found within symbolic logic. Aristotle held that any logical argument could be reduced to two premises and a conclusion. [2] Premises are sometimes left unstated, in which case, they are called missing premises, for example: Socrates is mortal because all men are mortal.
The second premise is an assertion that P, the antecedent of the conditional claim, is the case. From these two premises it can be logically concluded that Q, the consequent of the conditional claim, must be the case as well. An example of an argument that fits the form modus ponens: If today is Tuesday, then John will go to work. Today is Tuesday.
But a valid form with true premises will always have a true conclusion. For example, consider the form of the following symbological track: All meat comes from animals. All beef is meat. Therefore, all beef comes from animals. If the premises are true, then the conclusion is necessarily true, too. Now we turn to an invalid form. All A are B ...
Historically, begging the question refers to a fault in a dialectical argument in which the speaker assumes some premise that has not been demonstrated to be true. In modern usage, it has come to refer to an argument in which the premises assume the conclusion without supporting it. This makes it an example of circular reasoning. [1] [2]
From the example above, humans, mortal, and Greeks: mortal is the major term, and Greeks the minor term. The premises also have one term in common with each other, which is known as the middle term; in this example, humans. Both of the premises are universal, as is the conclusion. Major premise: All mortals die. Minor premise: All men are mortals.
Consider the modal account in terms of the argument given as an example above: All frogs are green. Kermit is a frog. Therefore, Kermit is green. The conclusion is a logical consequence of the premises because we can not imagine a possible world where (a) all frogs are green; (b) Kermit is a frog; and (c) Kermit is not green.
The first type of enthymeme is a truncated syllogism, or a syllogism with an unstated premise. [6] Here is an example of an enthymeme derived from a syllogism through truncation (shortening) of the syllogism: "Socrates is mortal because he's human." The complete formal syllogism would be the classic: All humans are mortal. (major premise ...