Fallacy of petitio principii, undue assumption and ignoratio elenchi are included under extra-logical fallacies. Petitio principii means assuming the very point that is required to be proved.
It is like arguing in a circle, so it is also called begging the question. What is intended to be proved is introduced into the premise. Suppose one argues that the earth revolves around the sun, because all known planets revolve around the sun.
Here the conclusion is assumed in the very premise “all known planets move around the sun” which is an enumerative universal. Thus when the conclusion is assumed in the premise, there arises the fallacy of petitio principii. This concept has been discussed in the context of uniformity of nature in little detail.
The fallacy of undue assumption arises when the premises are wrongly assumed. If the premise is false, then it’s very assumption will lead to a wrong conclusion.
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Fallacy of petitio principii also comes under this fallacy. Fallacy of undue assumption admits different forms. Its very common form is the assumption of a wrong premise. Most of the . Metaphysical speculations are based on this fallacy.
Matter is unreal, the world does not exist, motion is impossible are metaphysical assertions. These metaphysical assertions are drawn from undue assumptions of the metaphysicians. A wrong assumption or premise gives rise to a bizarre conclusion.