Monday, September 10, 2007

Validity and Soundness in a Modus Tollens: A Vital Difference

Mother Teresa: Come Be My Light, a book in which Teresa's letters and correspondence are presented by Brian Kolodiejchuk, has generated much interest in the spiritual life of one of the most remarkable women of the past century. From that book, David Van Biema of Time quotes from a letter Teresa wrote in 1959:
What do I labour for? If there be not God--there can be no soul--if there is no Soul then Jesus--You also are not true.
(David Van Biema, "Her Agony," Time 170 No. 10 (3 September 2007): 40)

Of course, this passage as a question and a series of hypothetical or conditional statements makes no assertion of deistic, agnostic, or atheistic belief. A conclusion could be entailed if the additional statement "Jesus is not true" (via modus tollens) or "There be not God" (via modus ponens) were present. As neither of these latter statements are asserted, we cannot validly infer an expression of any definite belief.

Nevertheless, a reader comments on the Time article by supporting the view that a purportedly atheistic Teresa would be a far more courageous individual than a purportedly doubting Teresa:
. . . people point to Teresa's lack of feeling the presence of Jesus as proof of God's existence. These people note her courage in persevering despite severe doubts. If she had been even more courageous, she would have admitted she was an atheist. Helping the poor without a belief in a heavenly reward is one of the greatest aspects of secular humanism.

(August Berkshire, "Inbox," Time 170 No. 12 (17 September 2007): 8).

Note that the structure of this argument (with an overly generous invocation of the principle of charity, neglect of the subjunctive tense, and the introduction of an inferred subconclusion), is modus tollens:

If p is true, then q is true.
q is not true.
Therefore, p is not true.

(Where p represents something like "Teresa is more courageous than someone who has doubts," and q represents "Teresa states she is an atheist.")

Since helping the poor without a belief in heavenly reward contextually implies such a person would be an atheist, and Teresa helped the poor with (presumably) having doubts about heaven--we have the vague appearance of a (valid) modus tollens.

Well, of course, all modus tollens arguments are valid. But since there is no evidence adduced for the statement that she admits to being an agnostic, much less an atheist, by any interpretation or translation of p and q, we have at least one false premise.

Consequently, even if we were to agree somehow to the questionable and murky translations, the argument in the Time letter is unsound. The best that Mr. Berkshire can hope for in this excerpt printed in Time is the assertion of a contrary-to-fact conditional statement.