One of the basic questions that comes up regarding issues of ownership in Jewish law is whether adam makneh davar she-lo ba la-olam – whether or not a person can buy or sell an object that is not in existence right now. Our Gemara presents this question as a disagreement between Rabbi Meir and the Sages, with Rabbi Meir ruling that something can be bought or sold even if it does not exist presently and the Sages ruling that such a thing cannot be bought or sold. The Gemara does limit Rabbi Meir’s ruling to a situation where the object is expected, even though it does not exist at this moment, e.g. if someone sells the rights to dates that will grow on a palm tree in the upcoming season.
In truth, when Rabbi Meir presents his position, he does not appear to require an expectation that the object will come into existence; he never mentions that the case of dates is what he is referring to in his ruling. If anything, the original case that Rabbi Meir discusses appears to be a case where the future of the situation is much in doubt – he presents his ruling in a case where a man asks a married woman to agree to marry him after her husband dies.
One approach suggested by the commentaries is that Rabbi Meir must be discussing an out-of-the-ordinary case, where, for example, the husband was on his death bed when the marriage proposal was made. Only there would Rabbi Meir rule that the marriage proposal has significance. Other rishonim argue that there are two issues at hand when Rabbi Meir discusses issues of a davar she-lo ba la-olam. Sometimes the issue is that the thing does not exist; sometimes the thing exists, but for one reason or another it cannot be acted upon at this time. Rabbi Meir ruling that adam makneh davar she-lo ba la-olam means that if we anticipate that the object will appear or if the object already exists and its status may change in the future, in both of these cases the decisions or activities made by the parties will have significance.
It should be noted that Rabbi Meir’s position is rejected and the accepted ruling is that ein adam makneh davar she-lo ba la-olam – that a person cannot buy or sell an object that is not in existence right now.