Let’s start with finding premises and conclusions. For the next few arguments, state what the premise is and what the conclusion is. Remember, you could have more than one premise and it may not be the first statement. You will only have one conclusion.
For the following arguments, determine what statement is the conclusion and what statement/s are the premises. You may state it or underline it. Don’t forget to look for indicator words as they will signal a conclusion or the premises. The next exercise, find the missing statement based on identification of the form.
1. God is that than which none greater can be conceived. If God were just an idea we could easily conceive of something greater, namely, a God who actually existed. Therefore, if God is that than which none greater can be conceive, then God must exist. (St. Anselm)
2. Titanium combines readily with oxygen, nitrogen, and hydrogen, all of which have an adverse effect on its mechanical properties. As a result, titanium must be processed in their absence. (World of Science Encyclopedia)
3. Artists and poets look at the world and seek relationships and order. But they translate their ideas to canvas, or to marble, or into poetic images. Scientists try to find relationships between different objects and events. To express the order they find, they create hypotheses and theories. Thus, the great scientific theories are easily compared to great art and great literature. (Giancoli, The Ideas of Physics, 3rd Ed.)
4. Every art and every inquiry, and similarly every action and pursuit, is thought to aim at some good. For this reason, the good has rightly been declared to be that at which all things aim. (Aristotle, Nicomachean Ethics)
5. Al Gore has a clear vision of where this nation must go with regards to energy policies. Anyone who has such a vision can write his ticket into the 21st century, and should be elected president. Al Gore is the right man to lead this country for the next four years. (Critical Thinking, Moore & Parker)
6. The fact that there was never a land bridge between Australia and mainland Asia is evidenced by the fact that the animal species in the two areas are very different. Asian placental mammals and Australian marsupial mammals have not been in contact in the last several million years. (Price and Feinman, Images of the Past)
- Now try to find the missing premise or conclusion by way of the forms, either valid or invalid, that you learned. Write it into the blank and tell us what form it fulfills.
1) All bachelors are unmarried men.
Ed is a bachelor.
2) If you are rich then I am single.
You are not rich.
3) All teachers work hard.
All teachers pay taxes.
4) Either today is Tuesday or it is Wednesday.
Today is Tuesday.
Exercises from S. Kelly, Thinking Well, an Introduction to Critical Thinking, and Patrick Hurley, A Concise Introduction to Logic.