It is argued that our attempts at knowledge cumulation have been flawed in four ways. They are the eroding of "empiricism" in clinical practice, the tendency towards paradigm passion and ethnocentricism, the failure to attend to "simple" measures of effect size, and the misuse of significance testing. It is recommended that speciality designations, the replacement of significance testing with point estimates and confidence intervals, the use of practical effect size statistics, the establishment of data repositories, and a renewed focus on replication would help resolve some of these problems.