I don't really understand the justification for "There is no silver bullet". How do we know? There may very well be a silver bullet, after all, we've already ha

I don't really understand the justification for "There is no silver bullet". How do we know? There may very well be a silver bullet, after all, we've already had some! Programming now using modern tools is at least an order of magnitude more productive than programming using punch cards or other methods used back in the day. Why are we so sure that all the silver bullets are behind us?