Chapter2: Clarifying Meaning
The place of Definitions in Critical Thinking
Knowing how to construct and evaluate definitions is vital to critical thinking.
(1) If we are trying to decide whether to accept or believe some claim then we need to make sure that
we understand the claim.
(2) Mastering an academic discipline requires understanding its key concepts.
(3) Solving problems requires knowing how to define the problem and potential solutions.
To claim that something is true is to assert it.(Asserting is not the same as supposing, considering,
assuming, pretending that, etc)
To assert is to claim that something is a fact or is true.
Proposition: We use complete sentences to assert something. (Make the claim that is true)
Not every complete sentence can be used to make an assertion. (Ex. Are oysters delicious?, Go Ryerson
These are used to ask questions or express support. They are not used to say something that is true or
So, they are not used to assert something.
The Assertion Test
To tell whether some proposition is asserted in a sentence, ask whether the sentence as a whole
could be true even if that Proposition were false.
If YES, then that proposition IS NOT asserted.
If NO, then that proposition IS asserted.
A conjunction is a sentence with an “And” in it. (Ex. Yonge is busy and Dundas is long)
A conjunction is true ONLY when BOTH of its conjuncts are true.
That is, if one of the conjuncts is false, then the entire conjunction is false. Disjunctions
A disjunction is a statement of the form (Either p or q)
Either John is late OR my clock is fast.
Either Jones OR the butler committed the murder.
What is asserted in a Disjunction?
A disjunction does not assert either disjunct. (Ex. In asserting that)
Either John is late or my clock is fast.
One is not asserting that John is late, and one is not asserting that John is late, and one is not
asserting that the clock is fast.
Rather: One is asserting that one, or both, of the disjuncts is true, even if we do not know much.
A conditional statement is a statement of the form
If p, then q
The Antecedent – what follows the word “if”
The Consequent – What follows the word “then”
What is asserted in a Conditional Statement?