It's useful for activists just to be out there to keep you mindful and not get complacent, even if ultimately you think some of their criticism is misguided.
We criticize a thinker more acutely when he advances a proposition that is disagreeable to us; and yet it would be more reasonableto do so when his proposition is agreeable to us.
It is the beginning of all true criticism of our time to realize that it has really nothing to say, at the very moment when it has invented so tremendous a trumpet for saying it.
I wouldn't be worth my salt if I weren't attracting some controversy and criticism. Everyone in the world who has done something in life has attracted criticism.
The sceptic will say, 'It may well be true that this system of equations is reasonable from a logical standpoint, but this does not prove that it corresponds to nature.' You are right, dear sceptic. Experience alone can decide on truth.