Good questions, and they point to major problems with logical positivism.
Today's descendents of the logical positivists are the empiricists like van
Fraasen. I find far more plausible the scientific realist approach which
lets you talk meaningfully about entities that cannot be directly observed
(with unaided human senses) or observed at all (they can be inferred by
For an excellent argument on this issue between the two viewpoints, see
IMAGES OF SCIENCE: ESSAYS ON REALISM AND EMPIRICISM, edited by Paul M.
Chuchland and Clifford A. Hooker. (Univ. of Chicago, 1985)
Max More, Ph.D.
President, Extropy Institute, Editor, Extropy