Ayer, “The Elimination of Metaphysics”

Thesis: Traditional disputes in philosophy are as unwarranted as they are unfruitful.

Main Argument:

P1: Metaphysical claims do not have any factual content.

1a: A claim has factual content only if there is in principle some sensory experience is relevant to its truth value.

[Verification Principle]

1b: No possible sensory experience is relevant to the truth value of metaphysical claims.

[Metaphysical claims are supposed to be transcendental—i.e., about the world beyond experience.]

P2: Metaphysical claims are not logically true/false.

[They are not trivially true or false in virtue of their truth-functional logical form.]

(P3): A claim is cognitively significant only if it either has factual content or is logically true/false.

[Logico-Empiricist Criterion of Cognitive Significance]

C: Metaphysical claims are not cognitively significant.

Verification Principle:

A. A claim has factual content only if there is some sensory experience that can establish its truth.

[Counter: “There is life on Alpha Centauri.”]

B. A claim has factual content only if there is in principle some sensory experience that can establish its truth.

[Counter: “All humans are mortal.”]

C. A claim has factual content only if there is in principle some sensory experience that can establish its falsity.

[Counter: “Some human is immortal.”]

The Argument Against First Principles:

Definition:

First Principles =df provide a certain basis for our knowledge (they are the foundations for a deductive system of beliefs)

P1: First Principles cannot be a posteriori.

1a: They cannot be empirical hypotheses/laws of nature. [These are not certain since they are in principle refutable by some empirical evidence.]

1b: They cannot be introspective judgments. [Either such judgments are not certain or there is no valid inference from them to claims about the external world.]

P2: First Principles cannot be a priori.

2a: All a priori truths are tautologies.

2b: From a tautology only other tautologies can be validly inferred.

2c: So if First Principles are a priori then they cannot validly support empirical claims—thus the resulting system would be either incomplete or lack certainty.

(P3) First Principles have to be either a posteriori or a priori.

[Logico-Empiricist Criterion of Cognitive Significance]

C: There can be no First Principles