Foucault argues that [the enlightenment] saw a cultural shift where madness was distinguished from reason and the civilised mind and where the mad were marked out and separated from mainstream society.
He argues that Europe began creating legal and social mechanisms to control those they deemed mad. Not least among these was the invention of the asylum and Foucault cites the 17th century as where lunatics began to be banished to these imposing human warehouses in what he called the 'great confinement'.
Except, it never happened. As the late great medical historian Roy Porter noted … there is no evidence of a systematic confinement of the mad in the 17th century.
… Madness and Civilisation isn't actually a very good history book.
Source: here