Class Notes (838,384)
Canada (510,870)
Philosophy (401)
PHIL 105 (81)
Lecture 7

Lecture 7 Notes

2 Pages
121 Views
Unlock Document

Department
Philosophy
Course
PHIL 105
Professor
Jill Mc Intosh
Semester
Summer

Description
Lecture 7 June 4, 2012 Why isn’t it enough to know, say, that an argument is valid in order to know whether you should accept its conclusion? How do you know whether an argument that would use predicate logic is intended to be valid or cogent? • If each of its premises and its conclusion can be written in one of the four standard forms for categorical statements, it is intended to be valid. • Four standard forms: All A are B, no A are B, some A are B, some A or not B. - Can “most A are B” be translated into one of these? No, it cannot, so the Four Rule Method cannot be used to test for cogency. - It is saying more than “some A are B”. (“some” means “at least one”) - It is not saying that some A are not B, since “most A are B” would be true even if “all A are B” were true. Ie. “Most of the students in this room are under 50”. – This isn’t false if all the students in this room are under 50. Can these claims fit into one of the four standard forms? • Every A is a B. = All A are B. • Only A are B. = All B are A. Consider the following two claims: 1. Dr. Mc owns a van. 2. Dr. Mc does not own a van. Could they be true at the same time? No. They are “in conflict” or inconsistent. They cannot both be false at the same time. 1. Dr. Mc’s one and only van is all orange. 2. Dr. Mc’s one and only van is all green. In conflict? (Ask – Could they both be true at the same time?) Yes, they cannot be true at the same time and there are in conflict. Could the both be false at the same time? Yes. They could be neither green nor orange. • If a pair of propositions could not both be true, but could both be false, they are contraries • In the first example? – If a pair of propositions could not both be true, but they also could not both be false, they are contradictories. 1. Dr. Mc has a dog. 2. Dr. Mc has a cat. They are not in conflict. How do we test for validity? • In sentential, we display the pattern and compare it to our tables. • Or we c
More Less

Related notes for PHIL 105

Log In


OR

Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Sign up

Join to view


OR

By registering, I agree to the Terms and Privacy Policies
Already have an account?
Just a few more details

So we can recommend you notes for your school.

Reset Password

Please enter below the email address you registered with and we will send you a link to reset your password.

Add your courses

Get notes from the top students in your class.


Submit