Obviously the teachers tell us that all kata movements are meant as a defence against some attacks, but until one sees and experiences it, this remains purely theoretical. Then you would need a partner who knows all the attacks necessary for the partnered kata...
I don't think that this is exactly true. Remember that there is partner practice in karate -- it's just not how kata are done. Experience in kumite gives you all that you really need to "see" the application of the kata, if you're having trouble imagining it.