No great genius is without an admixture of madness.

There is no great genius without a mixture of madness. [Lat., Nullum magnum ingenium sine mixtura dementia.]

The difference between genius and stupidity is that genius has its limits.

There was never a genius without a tincture of madness.

No great mind has ever existed without a touch of madness.

There is no great genius without some touch of madness.