# Philosophy 2340 Symbolic Logic

## Advice on Chapter 1 Problems

These are pretty straightforward, but there are a couple of things that sometimes confuse people.

General: When you get an answer wrong, the Grade Grinder will often offer a hint about what the problem might be. These are usually very useful, and you should read them carefully and try to make sure you understand what they're saying.

1.4: The first task is to translate the sentences into the blocks language. So, for example, the first one should be, not "a is a cube," but "Cube(a)". Make sure you follow the conventions of the language precisely. For example, make sure that all constants begin with a lower-case letter, and all predicates are capitalized.

World 1.5: I almost hate to write this, because it's something the authors apparently want you to discover by trial and error, but you can't put two large objects on adjacent squares. If two objects are adjacent, they can't both be large; if two objects are large, they must have at least one empty square between them.

1.9.5: Remember that everything you use in your translations must come directly from the "FOL" column of the table on p. 30. In particular, note that there is no predicate "Belonged," so you need to find a different way to express this. Also note that "p.m." does not appear anywhere in that column.

1.9.6: If you write something like:

2:00 < 2:05'

(with a little apostrophe or prime sign after the "2:05"), the Grade Grinder will tell you that this "isn't well-formed." That means it isn't a legal sentence of the language.

Why not? Because the ' symbol (the prime sign, or apostrophe, or single quote) in the table in

t < t'

is only there to indicate that we have two different variables here, t and t'. It could just as well have said

x < y

or

t1 < t2

So you don't want the ' symbol in your translation. The prime sign is part of the variable, not part of the name you replace the variable with in constructing a sentence.

Last update: August 24, 2012.
Curtis Brown  |  Symbolic Logic   |  Philosophy Department  |   Trinity University
cbrown@trinity.edu