Several of my recent Editorials have dealt with terminological/conceptual errors and confusions that have been all too prevalent among psi researchers. In this Editorial, I want to consider a related issue often raised about parapsychological concepts and explanation. Probably we’ve all heard the complaint that parapsychology’s core concepts have only been defined negatively, with respect to our present level of ignorance—for example, taking “telepathy” to be “the causal influence of one mind on another independently of the known senses.” Perhaps some (...) of you have even expressed that complaint yourselves. Of course, the assumption underlying those complaints is that this definitional strategy is a problem. However, it seems like a perfectly reasonable procedure to me, and I can easily accept the possibility that we might eventually learn enough about phenomena so defined that we can later construct better, detailed, and more informative analytical definitions. But at least as far as psi research is concerned, I consider it presumptuous—at our present (and considerable) level of ignorance—to proceed any other way. We hardly have the barest hint, based on all the available data, as to what psi is doing in the world (i.e., both inside and outside the lab). In fact, formal, experimental evidence has been particularly unilluminating. It has barely succeeded, if it’s succeeded at all, in convincing parapsychological fence-sitters that there are any genuine paranormal phenomena to study (I’ve explored some reasons for this in Braude, 1997). And it certainly hasn’t shed light on how pervasive, extensive, and refined psi effects might be, or whether effects of radically different magnitudes would be the result of substantially different processes. At best, typical quantitative research examines only straitjacketed expressions of phenomena that non-laboratory evidence suggests occur more impressively (if not flamboyantly) “in the wild.” So it strikes me as appropriately modest and circumspect to define “PK” (for example) as “the effect of an organism on a region r of the physical world without any known sort of physical interaction between the organism's body and r.” (For additional specific parapsychological definitions, see Braude, 2002). (shrink)