Homework #2 Logic Practice
I (50%). Say whether each of the following arguments is valid or invalid and sound or unsound by circling "valid" or "invalid" and circling "sound" or "unsound"
valid invalid a. 1. If anyone signs a contract voluntarily, then they are bound by its terms.
sound unsound 2. Mary Beth Whitehead signed the contract voluntarily.
thus 3. Mary Beth Whitehead is bound by the terms of the contract.
valid invalid b. 1. If anything is in Wisconsin, then it is in the U.S.
sound unsound 2. The University of Wisconsin is in the U.S.
thus 3. The University of Wisconsin is in Wisconsin.
valid invalid c. 1. Some philosophy teachers are over 40.
sound unsound 2. Dan Hausman is a philosophy teacher.
thus 3. Dan Hausman is over 40.
valid invalid d. 1. No dogs teach philosophy.
sound unsound 2. Dan Hausman teaches philosophy.
thus 3. Dan Hausman is not a dog.
valid invalid e. 1. All fetuses have a right to life.
sound unsound 2. If anything has a right to life then it is wrong to kill it.
thus 3. It is wrong to kill fetuses.
II. Consider the following critique of an argument:
"Those who maintain that surrogate motherhood contracts should be legally binding argue as follows:
1. If a contract is signed voluntarily by competent individuals and does not call for actions that ought to be illegal and its enforcement violates no inalienable rights, then it ought to be legally binding.
2. Surrogate motherhood contracts do not call for actions that ought to be illegal.
3. The enforcement of surrogate motherhood contracts violates no inalienable rights.
thus 4. If a surrogate motherhood contract is signed voluntarily by competent individuals, then it ought to be legally binding.
The conclusion is false, because surrogate motherhood contracts call for the sale of custody rights, which is illegal."
a. (10%) Is the argument in defense of the claim that surrogate motherhood contracts ought to be binding valid? Is it sound?
b. (10%) What is the logical structure of the critique of the argument consisting of statements 1-4? Can the critique be formulated as a logically valid argument?
c. (20%) Though it may require some changes in the critique, reformulate it as a logically valid argument in response to the argument stated in 1-4.
III (10%). Explain how a sound argument can fail to be rationally persuasive and how a rationally persuasive argument can fail to be sound.