This paper hypothesizes that the endowment effect has little to do with endowment—if we defined endowment as legal claim (what we call “proprietorship”). This paper hypothesizes that the endowment effect is rather the outcome of bonding or psychological attachment (what we call “ownership”). Most, if not all, the experimental work in the economics literature involve a major confound between proprietorship (legal claim) and ownership (bonding). We run the standard workhorse experimental design—viz., the exchange of mugs and pens of Monash University—while separating ownership from proprietorship. We predict: i) the endowment effect appears even when there is no proprietorship (just mere ownership); ii) the endowment effect appears in the case of proprietorship of both items—which allows us to reason that it is the result of difference in ownership; ii) the endowment effect disappears in the case of proprietorship of both items when the participants see the items simultaneously—which allows us to reason that the simultaneity has expunged the ownership effect.