Some Arguments in the Nicomachean Ethics
An argument is a presentation of reasons or evidence that support some conclusion, which is the point argued for. The statements that express this evidence or reasons are called premises.
Example:
2. All humans are mortal
The upper two statements, “Socrates is human,” and “All humans are mortal” are the premises. “Socrates is mortal” is the conclusion. This argument is written in what we will call standard form, with the premises listed first, then a horizontal line, then the conclusion. In this example, the premises, if they are true, give conclusive proof that the conclusion is true, too. An argument like that is called valid.
An argument where the premises provide strong evidence for the conclusion, but don't absolutely guarantee it, is called inductively strong. For example:
1. Almost all students in this class are freshmen or sophomores.
2. It is very rare for a freshman or sophomore to have grandchildren.
3. Therefore there are few (or no) grandparents registered for this class.
An argument might also provide very little support of a conclusion, in which case it is called weak. For example, the premises in the following argument give very little evidence that the conclusion is true, even if those premises are true:
1. Blonds have fun.
2. I have fun
3. Therefore, I am blond.
Question: Change the first premise of this argument to "Only blonds have fun." Would the argument then be valid or invalid?
Philosophers often try to organize the support for their conclusions into valid arguments. This is not always possible, especially when the conclusion is drawn from experience or is the result of a scientific investigation. The advantage of presenting a valid argument is that you will be able to reduce all debate to answering a single question: are the premises true? A valid argument with true premises must also have a true conclusion. Here is a presentation of some of Aristotle's reasoning about happiness in the form of a valid argument:
1. The best good is the most complete.
2 The most complete good is (a) chosen for its own sake (in other words, the most complete good is an ultimate or intrinsic good) and (b) never chosen as a means to get something else that is good.
3. Happiness is an ultimate good
4. No one ever chooses happiness for the sake of some other good.
5. Therefore, happiness is the best good.
Here is series of valid arguments, where the conclusion of some step in reasoning is used a premise in the next step:
1. If virtues arose by nature then almost every one would have almost all virtues.
2. Many people lack many virtues
3. Therefore, virtues do not arise by nature.
4. But all our characteristics arise either by nature or by habit.
5. Hence, virtues arise from habit.
The first argument here is 1, 2, therefore 3. The second is 3, 4, therefore 5.
Question: Is the following argument valid? (note that an argument could be valid, even if the premises are not actually true).
1. No philosophy majors are bank robbers.
2. No philosophy majors are accountants.
3. Therefore, no accountants rob banks.