§3 Inductive Reasoning

Unlike deductive reasoning, which aims for absolute certainty, inductive reasoning focuses on probability and evidence. An inductive argument does not claim that the conclusion must be true, but rather that the premises make the conclusion likely or well-supported.

3.1 Strength (The Sliding Scale)

In deduction, an argument is either valid or invalid—there is no middle ground. In contrast, inductive strength exists on a sliding scale. We evaluate how much support the premises provide for the conclusion.

• Strong Inductive Argument: If the premises were true, it would be highly probable (typically over 50%) that the conclusion is also true.

• Weak Inductive Argument: The premises do not provide enough support to make the conclusion probable, even if they are true.

Example of a Strong Argument:

P1: Most students at Green River College use the campus Wi-Fi.

P2: Sarah is a student at Green River College.

$\therefore$ C: Sarah probably uses the campus Wi-Fi.

Because “most” implies a high probability, this argument is structurally strong.

3.2 Cogency (The Standard for Truth)

Just as deduction has “soundness,” induction has cogency. For an inductive argument to be truly successful in convincing someone, it must pass two tests:

1. It must be Strong: The logical probability must be high.

2. The Premises must be Actually True: The evidence provided must be factually correct.

If an inductive argument is strong and its premises are actually true, it is considered cogent. If it fails either of these (it is weak or has at least one false premise), it is uncogent.

3.3 The Total Evidence Requirement

A unique feature of inductive reasoning is the Total Evidence Requirement. Unlike deduction, where a valid argument remains valid regardless of new information, an inductive argument can be weakened or strengthened by new evidence. To be truly cogent, an inductive argument must not ignore “available, relevant information” that would undermine the conclusion.