(manuscript of Leibniz's Monadology)
Scepticism may come in all shapes and sizes, but two of its forms are most important for me, the second more than the first:
1) Scepticism as to the external world. The question if the computer I am typing on right now really exists or is a mere illusion. Is it a serious question? On the one hand it would be difficult to say how a real computer can differ from its illusion, which looks exactly the same, feels the same to the touch, etc. If a duck looks like a duck, walks like a duck and quacks like a duck, it probably is a duck. On the other hand films like Matrix or Inception make a powerful case for the validity of the question about the real existence of the external world.
2) Scepticism about the existence of other minds. This is not the same question. The world may be a mere illusion and all my perceptions may be false. But if other minds exist, they may have the same illusions. And they do not need to exist in the outer physical world. They can be monads like in Leibniz’ monadology which perceive their own perceptions synchronised with my own and everyone else’s perceptions in a special harmony. But as long as they are feeling and suffering beings I fell compassion for them, whether they are spatial or not.
That’s why the second question is more important for me. If I do not recognise the existence of other minds (even if I question the existence of the external world) I cannot feel compassion for them and build a Hume-style ethics based on empathy with my fellow beings.
