Doyle Online Writing Lab
Aristotle & Logic: Syllogisms & Inductive Reasoning
Syllogistic logic and inductive logic are key forms of persuasion in the Ethics. According to Aristotle, scientific knowledge "starts from what is already known...[and] proceeds sometimes through induction and sometimes by syllogism" (VI.3 p. 140). The difference between syllogism and induction is as follows: "induction is the starting-point which knowledge even of the universal presupposes, while syllogism proceeds from the universals" (V1.3 p. 140).
A. Syllogisms (a type of Deductive reasoning)
Syllogisms consist of three parts:
- general statement ("universal")
- particular example
An example from Reeve's Practices of Reason, p. 12
- All plants in which sap solidifies at the joint between leaf and stem in autumn are deciduous.
- All oak trees have sap that solidifies at the joint between leaf and stem in autumn.
- Therefore, all oak trees are deciduous.
Another example from a Humanities 110 lecture (12/1/95):
- One should not seek delights that violate the sacred guest/host relationship
- (a) I am now a guest in Helen's house; (b) fulfilling our reciprocal desire would be delightful; (c) but she is the wife of my host
- Therefore, making love with Helen would be a violation of the guest/host relationship, and I should not do it.
Sample hypothetical example from a student paper
- To be rational means one must act consistently, take multiple factors into account, and choose what is "best".
- Antigone acts consistently, takes multiple factors into account, and chooses what is "best".
- Therefore, Antigone is rational.
An example you have found in the Ethics:
B. Inductive Reasoning
According to Daniel Sullivan, "inductive reasoning involves a transition from the sensible singular to the universal" (Fundamentals of Logic 114). For example:
And this fire warms,
And this fire warms, etc.
Sample inductive reasoning from a hypothetical student paper Antecedent:
In The History, Thucydides dumps on confidence
In The Bacchae, Euripides dumps on confidence
Consequent: All Ancient Greeks thought confidence was bad.