Dear Sirs,

Zepf's comparative critique of attachment theory (2006) is scholarly and exhaustive. But he addresses this question, as he puts it in his subtitle, ‘from an epistemological and from a Freudian viewpoint.’ To the extent that psychoanalysis is a science (and he writes as if it were), major scientific ideas or differences about theories have not been decided primarily upon theoretical debates, neither metapsychological (as Zepf says) nor metaphysical. Kuhn, particularly in The essential tension (1977), and Polanyi (1958) articulate criteria that scientists within a field decide upon the ‘correctness’ or usefulness of competing theories.