During the transition of the XIX to the XXth century, several changes took place in the dominant moral psychiatric paradigm. In the movement, that opposes the former romantic and normative vision of behaviour and intentions, the primacy of observation and description emerges as a superior clinical method, organizing knowledge and investigation. Kraepelin in one of the main figures that emerges, with a remarkable masterpiece, his "Treatise of Psychiatry", including several editions, each one resulting in reformulations according to the new data he obtained. Comparing Kraepelin's work - or other contemporary authors - with posterior essays on thought and language in shizophrenia would be incongruous, because the irreducibility of a clinical to an experimental method. The aim of this paper is merely to show the relation between clinical descriptions and the resulting hypothesis or constructs. Description is viewed as a systematic exploration of the psychopathological reality and an important source of scientific intuitions. This is what has happened with the work of Kraepelin, Bleuler and many others, from which we can extrapolate the ideas for knowledge produced in laboratorial context. In particular, we shall review investigation data about thought and language, produced between the sixties and the eighties, a very fertile scientific period in this area of knowledge and, which has, almost disappeared. In fact, today's literaure about thought diosorder in schizophrenia is based predominantly on the neuropsychological paradigm with the use of test batteries that evaluate cognitive deficits. The importance of this perspective is that it enables the development of response indicators with the psychopharmacological therapies and the implementation of rehabilitation programs. However, it doesn't contain the richness of the period mentioned earlier. We chose some of the particular aspects of cognitive functioning to illustrate the influence of Kraepelin's papers on the more recent studies.