Excerpts from van Stigt's "Brouwer's Intuitionist Programme"

Brouwer-communication

Brouwer's philosophy of language starts from the conviction that direct
communication between human brings is impossible. His chapter on "Language"
in "Life, Art and Mysticism" starts as follows: "From Life in the Mind
follows the impossibility of communicating directly with others... Never
has anyone been able to communicate directly with others soul-to-soul."
The privacy of mind and thought and and the hypothetical existence of minds
in other human beings, who are no more than the Subject's mind-creations,
"things in the exterior world of the Subject" rule out "any exchange of
thought".

...

As to language as a means of communicating mathematics to other individuals,
there is no basis for agreement between the constructive thought-processes
of different individuals represented in a "common language." To the Subject
other individuals are "things," creations of his Exterior World, and the
existence of other minds similar to his own "mere hypothesis." And even if
the existence of other minds were to be conceded, there is no guarantee that
common words would represent the same thought-construction in the private
worlds of different individuals.