Prabhupada further explained that the science of the soul cannot be studied academically in a university. When one is studying science and wants to get a particular result, which can be obtained only by performing a scientific experiment, then he has to go to the laboratory and perform that experiment. Similarly to obtain the result of spiritual knowledge, which is vijnana (realized knowledge), one has to perform certain activities which are conducive for understanding the existence of the soul, otherwise it is just theoretical knowledge.
LFD Vol 3,Uprooting Sinful Activities, Pg 198, 3rd paragraph