Madness is the confusion of reality with the words in one's head. Where perception and raw experience have been ousted, insofar as humanly possible, by incessant interpretation of perception. One is in a permanent state of selfhood, but while this "selfhood" may suggest that this state is one of reality, it is in truth imaginary but invested with the semblance of reality by the fact of the mind-body organism that is conceiving of it. Reality for the subject of the madness is, to a catastrophic level, a matter of words, an incessant interpretation of reality, but this human subject is, despite his best efforts, himself a real living being, and so is potentially able to invest and manifest a dreadful 'external' dynamism to the mad, false ideas.
Thus the dangers of all matters of false collective idealism- of some political bent- where the subjects of the malaise of thought attempt to force reality into the dimensions and parameters of thought which they have decided life really ought to fit into if it is to be truly reality or the desired version of such. And since the subject, speaking in the singular, is certainly bound to find in reality in the flesh immense obstacles to the reality in his head, the most extreme measures will be used to effect the necessary changes, and given the lack of success he is bound to meet with, ever more extreme measures to push obstinate life in the desired direction.
This all-pervading idealism or madness is not to be confused with the practical healthy idealism of someone who, for instance, thinks efficient sewerage systems are desirable for a community and effects the necessary changes. Here the ideas are intelligent fragments of life, whereas in the former case life as a whole is substituted for an idea of itself, some artificial simulacrum.