It is a commonplace in our exposition of our right and our connection to Eretz Yisrael that the Bible is our deed to the land. It is interesting to look at how the Torah itself articulates our earliest roots in the land. Here are some (though not all) of the relevant passages in Genesis: 12:1 Go forth to the land that I will show you. 12:7 I will assign this land to your offspring. 12:8 he pitched his tent and he built there an altar 13:17 Up, walk about the land, through its length and breadth, for I give it to you. 15 the covenant between the pieces: To your offspring I assign this land 21:25-30 Abraham and Abimelech the Philistine swear an oath dividing possession 21:33 Abraham planted a tamarisk tree 23 Abraham purchases the cave of Machpelah in Hebron as a burial site, and buries Sarah there 28:16 Abraham renames Luz as Bethel 33:19 The parcel of land where [Jacob] pitched his tent he purchased from the children of Hamor, Shechems father, for a hundred kesitahs. 37:1 Now Jacob was settled in the land where his father had sojourned
It seems from this catalogue of symbolic acts of possession that perhaps even in ancient times, this was a topic fraught with some discomfort. What in fact gives any people the moral right to live on the land they live on? Is the only proper claim some primeval division, whereby we should all live where our ancestors lived, since the beginning of human habitation? And if this is unrealistic, then how do we prioritize the claims of peoples who migrate to, conquer, or are driven into lands where they were not born?
The predominant answer in Genesis and later interpretation is that God created the earth and therefore He has the right to divide it up and assign peoples to their lands and He has the right to change his mind, and re-assign peoples, based on their behavior. This works if you believe in a God who does things like that; it is a problem for secular Zionists who dont believe in God.
But even in the context of the Torah itself, this seemingly unshakable argument must not have been sufficient, for the text takes the trouble to detail (see the list above) a number of other methods of taking and claiming possession of land: pitching a tent (i.e., squatting/homesteading/settling); building an altar (sanctifying); walking about (getting to know); signing a treaty; planting a tree; purchasing for cash; establishing a cemetery; naming places. Each of these represents a different symbolic way of staking a claim to the land, of defending our right to live in the land and control it.
This multiplicity of approaches to taking possession of land makes me suspect that even the Torah had questions about the absoluteness of such possession. Indeed, maybe the more important question, then and now, is: OK, so we can claim possession; but what does that mean? What are we entitled to do with the land now that we possess it? What rights/obligations does possession give/impose upon us with respect to the inhabitants of the land? with respect to the stewardship of the natural resources of the land? with respect to sharing possession with others? If we bought it, can we sell it? If it is ours, can we pollute it? If it is for us, can we throw everyone else out?
It seems to me that the argument over claims of possession is bottomless, and ultimately perhaps not useful. The important argument is over what that possession means to us, to the land, to the others who live on it.