In his important and influential paper “Empiricism, Semantics and Ontology” Rudolf Carnap¹ ties the use of abstract entities to linguistic frameworks and distinguishes between external questions, i.e., questions about the choice of a framework, and internal questions, i.e., questions concerning the truth and falsehood of the statements which are formulated within a certain framework. External questions, he says, are decided in a practical way, by testing the efficiency of a given framework. Internal questions are either questions of logic or of empirical accuracy. Quine² “espouse[s] a more thorough pragmatism.” By this he means that external and internal questions are to...

My predecessor, who in this hall gave the first Arthur Holly Compton Memorial Lecture a year ago, was more fortunate than I. He knew Arthur Compton personally; I never met him.¹

But I have known of Compton since my student days in the nineteen-twenties, and especially since 1925 when the famous experiment of Compton and Simon² refuted the beautiful but short-lived quantum theory of Bohr, Kramers, and Slater.³ This refutation was one of the decisive events in the history of quantum theory, for from the crisis which it created there emerged the so-called new quantum theory—the theories of Born...

Just what is the problem of identifying an intervention or treatmenttof one sort or another as a placebo for a target disorder D? One set of circumstances, among others, in which the need for such an identification may arise is the following: After the administration oftto some victims ofD,some of them recover from their affliction to a significant extent. Now suppose that there is cogent evidence that this improvement can indeed be causally attributed at all to some factors or other among the spectrum of constituents comprising the dispensation of ι to a patient....

It has been said that the single most difficult thing to do in the world is to write with clarity and style. (It has also been said that fine writing is easy: One simply stares at the blank paper until the sweat on one’s brow turns to blood.) Paul Meehl writes with the elan of no one else in our field, and to read him is to experience an aesthetic rush along with the inevitable intellectual jolt. Indeed, while waiting for my own sweat to congeal, I sometimes engage in a peculiar form of bibliotherapy: I read a piece or...

In stories on time travel, writers often lead us to wonder what one who alters the past would find upon one’s return to the present. One can reverse this mental exercise; if the present were different, how would antecedent events have differed?

In 1986, Paul Meehl said:

People sometimes ask me whether I am disappointed by the relatively feeble impact of that book [clinical versus statistical prediction] and the many studies that were stimulated by it. . . .I really didn’t expect people to think rationally about it. (p. 375)

Imagine now the events that would have preceded a statement...

More than 30 years ago Meehl (1957) posed an important question in the form of paper with the catchy title “When Shall We Use Our Heads Instead of the Formula?” His answer was that if we have a formula, then we should use our heads only “very,veryseldom.” The “head” in the title of the paper refers to the processing of clinical data intuitively, the “formula” to any form of nonjudgmental, mathematical, statistical, or mechanical handling of the same information.

Meehl’s main objective in his paper was to alert clinical psychologists to the idea that in making predictions about...

Following Hume’s (1740, 1748) convincing argument that causal inferences based on everyday experience cannot be empirically verified, many philosophers agreed with Mill that “observation, in short, without experimentation (supposing no aid from deduction) can ascertain sequences and co-existences, but cannot prove causation” (1843, p. 253). Others have been less restrictive and argued that causality can be inferred on a statistical basis granting certain assumptions — e.g., “that there is no third event that we can use to factor out the probability relationship between the first and second event” (Suppes, 1970, p.10) — assumptions that are subject to empirical verification, or at least...