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Aristotle’s Practical Syllogism, Dr. Peter Krey, Jan. 29th 2004

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Aristotle’s Practical Syllogism

Dr. Peter Krey, Jan. 29th 2004

David Hume argues that you cannot get from the “is” to the “ought” via logic. Aristotle, however, works out a practical syllogism that answers to desire and could have a standard of right desire. Is it valid?

Aristotle’s Practical Syllogisms[1]

The major premise of a practical syllogism is universal, a general rule. The minor is particular, the application of the rule to the case at hand. The application really quires two syllogisms.

Dry food is good for everybody. Syllogism One.

I am somebody.

Therefore, dry food is good for me.

Dry food is good for me. Syllogism Two.

This stale loaf is dry food.

Therefore, this stale loaf is good for me.

Aristotle notes that action has to do with particular things. One universal has to be predicated about the thing itself and the other about the person.

The major premise could be an opinion, while the minor could deal with particular things, which are perceived. ANow when the two premises are combined, just as in theoretical reasoning the mind is compelled to affirm the result of the conclusion, so that in the case of practical premises you are forced at once to do it. For example, given the premises, All sweet things are to be tasted” and “Yonder thing is sweet” – a particular instance of a general class -, you are bound, if able and not prevented, immediately to taste the thing.” Aristotle continues that you can have a negative universal rule: Avoid sweet things.” But if a strong desire is present, then you eat the sweet thing. It is the desire not the opinion that is really opposed to the right principle in an unrestrained person.

All sweet things are to be tasted”

and “Yonder thing is sweet”

Therefore, yonder thing has to be tasted. (As you dish in).[2]

Does Aristotle’s Syllogism disprove Hume? Observe that two syllogisms are needed to complete the application from principles to actions.

Another take on Aristotle and the Practical Syllogism

March 9, 2005

There has to be a clear distinction between an abstract proposition and concrete action. Between these positions, there is the possibility of considering the utterance of the proposition as a speech act, but let’s not proceed into the Philosophy of Language and its theory of action right now.

The study of correct reasoning is logic; the study of correct action is ethics. Aristotle bases his practical syllogism on his conviction that correct action should be guided by correct reasoning, which would make such action rational and therefore ethical.

But Aristotle himself in his Nicomachean Ethics states that ethics is not precise and often cannot completely be subsumed under reason, because actions are often irrational. In addition the history of actions that are inside events do not follow each other in a logical way, but can only be reported in the science of time, which we call history.

But for the case when correct behavior is guided by correct reasoning, that is, when rationality goes beyond ideas and into actions, Aristotle fashions a practical syllogism to capture the unit of thought and action in an argument.


[1]Aristotle, Nicomachean Ethics, VII:iii.6-9, (Loeb Classics vol. XIX), (Cambridge: Harvard University Press, 1994), p. 388f.

[2]Ibid., p. 391-392.

Written by peterkrey

July 14, 2008 at 7:35 pm

Posted in Logic

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