In an article in the Millennium issue of this Journal on the changed views on anti-social conduct disorders in children, Matthys states that Hart de Ruyter - the first professor of child and adolescent psychiatry in the Netherlands - ascribed the etiology of these disorders one-sidedly to unfavourable environmental influences only. He also assumes this one-sidedness to be typical of the psychoanalytically oriented clinicians of those days. Matthys' idea is widely held in child psychiatry today, but it is in my opinion incorrect. In the present article Hart de Ruyter's approach is reviewed and it is shown that he had in fact a broad, 'modern' view. In this view the interaction of child-specific and environmental factors is emphasised. The origins of the present days' misconceptions are discussed. This leads to a short discussion of related issues, which are basic to psychiatry now and then: the dualistic position, the 'multi-conditional' or biopsychosocial approach and the tendency to one-sidedness. I therefore draw the conclusion that Hart de Ruyter's and influential psychoanalytically oriented contemporaries' views on the etiology of (child) psychiatric disorders are not one-sided and out-dated. Their valuable clinical insights, which are complementary to current research findings, should not be lost.