How to define a Malkavian... Insane? Prophetic? Or just on a different level of conscious than the rest of us? It is hard to say.
One thing for certain is that they possess power over sanity itself. From the moment of their embrace each Malkavian gains some form incurable insanity. But they also gain gifts of insight that other Kindred both envy and fear. They look into the unknown and find meaning.
All Malkavians are connected to each other, they all possess a vast sixth sense, a network between the minds of every member of the Clan– and they all have insights beyond any mortal capacity to understand.
But what is insanity? As with all derangement's for any human or Kindred each Malkavian is unique. Being “insane” does not necessarily mean stark raving lunatic. A derangement can have many causes and effects. A Malkavian could be fearful of being forgotten, and if they are being ignored lash out physically, or maybe they would just break out in song and dance. Or it might be the multiple personalities of old, a compulsion like kleptomania or megalomania.
The reality is that most people have them but the derangement a Malkavian possess usually helps define them.