The Challenges of
the Is-Ought Fallacy

In his thesis, the philosopher David Hume (1711-1776) reasoned that a moral "ought or ought not" cannot be derived from an "is" (what is - such as a biological or empirical fact). This became known as the Is – Ought Fallacy.

He said, "conclusions about what someone ought to do cannot be validly derived from any set of premises about what is the case empirically." Hume’s arguments were based on the principle that valid arguments cannot have conclusions containing concepts that did not appear in any of the premises.

For example:

1. The premise: whales are endangered species.

2. The ought: therefore humans ought to limit the killing of whales.

The Is – Ought Fallacy is the improper logic in concluding that humans should morally do something based on a fact of whales.

To avoid the Is – Ought Fallacy, the above example should have a different premise:

1. The premise: humans ought to preserve our natural resources.

2. The ought: therefore humans ought to limit the killing of whales.

The Is – Ought Fallacy is the error in logic of deriving a prescriptive statement from only descriptive premises.

To say what is the case and to say what ought to be the case are two unrelated matters. What is happening is not the same as what ought to happen. Behaviors that can be described do not mean that the behavior can be prescribed as a moral standard.

Darwin, and Spencer’s theories fail because of the Is - Ought Fallacy. Sociobiology and Meme Theory avoid this fallacy, because no attempt is made to define normative statements with empirical facts.

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