The main purpose of this chapter is to criticize the position called “psychologism.” This position is attributed to John Stuart Mill, which claims that human actions and institutions can be explained by a psychology of human nature. Popper’s position is that they cannot; that social phenomena are sui generis, i.e., autonomous. I will not rehearse his arguments, with which I agree, but introduce my own.
Consider the case of feral children, who are by assumption normal, except for lacking a human language. Watch the following video below about such children:
The video asks whether feral children are “human.” In one sense, of course, biologically, feral children are human beings. The question is really whether they are “persons,” or “human” in the way we are. By my criterion, a person is anything with which one can make agreements. And agreements are possible only with a language. So, the origin of society as we have it, is possible only with language. Subtract language from a person, and you get a feral human being.
One interest in studying feral children is to understand under what conditions learning a language is possible. And the hypothesis is that there is a critical period of early life when learning a language is possible — something like the phenomenon of imprinting. And when that window of opportunity is passed, learning a language does not occur.
The mystery is how languages originate. And the only clear fact is that language is a social phenomenon. Other than the behavior of a feral child, all other actions of human beings are imbued with language and human institutions. Thus, if Descartes were more reflective, he would have realized that his skepticism was possible only in language; specifically, the statement “I think therefore I am” is in language. He could have concluded “I think therefore I am using a language.”
Popper concludes — and I agree — that what passes for psychology [of a language using human] is imbued with sociology.