Some people have the strange, sometimes religiously motivated, belief that human intelligence has some vague magical property which by definition can't be reproduced in mere physical machines.
Otherwise it's just arguing about how difficult AI will be which is very hard to estimate. Some people look at previous failures and lack of progress in AI and extrapolate from that. But progress is rarely linear and computers are only now getting fast enough to handle the really cool stuff.
Otherwise it's just arguing about how difficult AI will be which is very hard to estimate. Some people look at previous failures and lack of progress in AI and extrapolate from that. But progress is rarely linear and computers are only now getting fast enough to handle the really cool stuff.