The criteria people typically use to distinguish the more reliable ‘hard sciences’ from the less reliable ‘soft sciences’ do not match our understanding of which is which. Instead, I think that the difference lies in the history of the fields. For hard sciences, the science precedes the community. For soft sciences, the community precedes the science. Hard sciences have norms of empiricism. Soft sciences try to import rules of empiricism. If you want to harden a science, it is more important to grow the norms than to establish the rules. One way to accomplish this is to require early career scientists replicate at least one major result in their field as part of their education.