One answer has to do with equating essentially contested, or holophrastically indeterminate, words or concepts- like Justice, or Capabilities, or Entitlements- with mathematically rigorous Sets and then looking at situations where we can good-faith agree that elements of a certain type belong in the Set in question. Our naive intuition is that, once a sufficient sequence of such elements is admitted, then some structural feature of the Set will become evident such that all our theorems can be 'relativised' w.r.t that set and a Bernays (second order) Reflection Principle obtains such that we have an assurance that the Set as a whole will exhibit the property we have painstakingly discriminated and what's more all our Knowledge is relevant to it and every correct form of Reasoning applicable to it.
If words and concepts are essentially ontologically dysphoric- i.e. not at home in this world- and thus if the Sets that describe them bear no relation to the 'Universal Set' (V) of all that is- no objection can be raised, other than the obvious one- viz. why pay Professors to spout Schizophrenic shite when our Lunatic Asylums supply a better product for free?
Suppose words and concepts, save when used disingenuously, aren't gaping wormholes into madness, then any Set they define must be a subset of V. However, in that case, either some Set of algorithms exist, within the Universal Set, which with provable consistency partition V so as to yield the Set you are interested in- which is impossible by Godel's second incompleteness theorem- or there is no provably consistent algorithmic method of wholly distinguishing that Set within V.
As Godel put it-
I suppose, if one still wants to gain the academic respectability of Mathematics, one could still do so by invoking Fuzzy Set theory- indeed, there are some approaches to Entitlements which do so- but, while this might be sensible- and the sort of back-room drudgery Bureaucrats ought to be doing for the good of their souls- what it isn't is Sen-tentious.
Consider the following-
Well, 'opportunities' are what Evolution has designed us to search for on an unknown, unpredictable, fitness landscape. Similarly 'rights' are co-evolved and subject to even more uncertainty including strategic uncertainty.
As for the Law- it is scarcely static and unchanging.
In the case of the Bengal Famine, which Sen studied, it wasn't the Law 'which stood between food availability and food entitlement'. On the contrary, the elected Govt of Bengal could have implemented the Bengal Famine Code- or at least acknowledged that a Famine caused by food availability deficit existed instead of pretending them evil Hindu Money-lenders were hoarding all the food.
Sen's hilarious theory is that workers in the Cities were so gluttonous and callous that they ate 5 times as much rice as previously and stood around with jutting bellies sneering at their own brothers and cousins from the countryside who had come staggering into Calcutta only to collapse and die in the streets.
Yes, there was an Entitlements type failure- it became impossible to sell or mortgage land while the Japs (aided and abetted by Subash Chandra Bose's Indian National Army) were at the door- and, no question, the Army and the Administration worsened things initially, till an Army man became Viceroy- but that wasn't the root of the problem.
The fact is, in a rain fed Agricultural economy (as opposed to a 'no escape' zone of fertility) , Entitlements create Famines.
Well, the evolutionary stable strategy- absent belief in Entitlements- is to have highly diversified food resources and also to maintain mobility. Thus if one or two or three food sources collapse, agents can still survive or walk away. Should land become scarce- head hunting is a good Zahavi type signal.
The alternative- viz. producing a surplus to support a class of fungible asset producers- depends crucially on the notion of Entitlement- legal, contractual, theological, moral or what have you.
The Law guarantees that food availability deficit will translate into food entitlement collapse. Why? It fools people into investing in, if not an otologically dysphoric, then a wholly naked Ponzi scheme rather than, as Evolution dictates, making a Career Move into Head Hunting.
Like Charu Mazumdar, Kanu Sanyal, Jangal Santhal et al.