§3. If now we turn again to the political question, from which we diverged, we see that we have obtained from the preceding discussion one of the criteria of the justice of laws which we were seeking---viz. that they must avoid running counter to natural and normal expectations---: but we see at the same time that the criterion cannot be made definite in its application to private conduct, and it is easy to show that there is the same indefiniteness and consequent difficulty in applying it to legislation. For Law itself is a main source of natural expectations; and, since in ordinary times the alterations in law are very small in proportion to the amount unaltered, there is always a natural expectation that the existing laws will be maintained: and although this is, of course, an indefinite and uncertain expectation in a society like ours, where laws are continually being altered by lawful authority, it is sufficient for people in general to rely upon in arranging their concerns, investing their money, choosing their place of abode, their trade and profession, etc. Hence when such expectations are disappointed by a change in the law, the disappointed persons complain of injustice, and it is to some extent admitted that justice requires that they should be compensated for the loss thus incurred. But such expectations are of all degrees of definiteness and importance, and generally extend more widely as they decrease in value, like the ripples made by throwing a stone into a pond, so that it is practically impossible to compensate them all: at the same time, I know no intuitive principle by which we could separate valid claims from invalid, and distinguish injustice from simple hardship. 
But even if this difficulty were overcome further reflection must, I think, show that the criterion above given is incomplete or imperfectly stated: otherwise it would appear that no old law could be unjust, since laws that have existed for a long time must create corresponding expectations. But this is contrary to Common Sense: as we are continually becoming convinced that old laws are unjust (e.g. laws establishing slavery): indeed, this continually recurring conviction seems to be one of the great sources of change in the laws of a progressive society.
Perhaps we may say that there are natural expectations which grow up from other elements of the social order, independent of and so possibly conflicting with laws: and that we call rules unjust which go counter to these. Thus e.g. primogeniture appears to many unjust, because all the landowner's children are brought up in equally luxurious habits, and share equally the paternal care and expenditure, and so the inequality of inheritance seems paradoxical and harsh. Still, we cannot explain every case in this way: for example, the conviction that slavery is unjust can hardly be traced to anything in the established order of the slave-holding society, but seems to arise in a different way.
The truth is, this notion of `natural expectations' is worse than indefinite: the ambiguity of the term conceals a fundamental conflict of ideas, which appears more profound and far-reaching in its consequences the more we examine it. For the word `natural', as used in this connexion, covers and conceals the whole chasm between the actual and the ideal---what is and what ought to be. As we before noticed, the term seems, as ordinarily used, to contain the distinct ideas of (1) the common as opposed to the exceptional, and (2) the original or primitive as contrasted with the result of later conventions and institutions. But it is also used to signify, in more or less indefinite combination with one or other of these meanings, `what would exist in an ideal state of society'. And it is easy to see how these different meanings have been blended and confounded. For since by `Nature' men have really meant God, or God viewed in a particular aspect---God, we may say, as known to us in experience---when they have come to conceive a better state of things than that which actually exists, they have not only regarded this ideal state as really exhibiting the Divine purposes more than the actual, and as being so far more `natural': but they have gone further, and supposed more or less definitely that this ideal state of things must be what God originally created, and that the defects recognisable in what now exists must be due to the deteriorating action of men. But if we dismiss this latter view, as unsupported by historical evidence, we recognise more plainly the contrast and conflict between the other two meanings of `natural', and the corresponding discrepancy between the two elements of the common notion of Justice. For, from one point of view, we are disposed to think that the customary distribution of rights, goods, and privileges, as well as burdens and pains, is natural and just, and that this ought to be maintained by law, as it usually is: while, from another point of view, we seem to recognise an ideal system of rules of distribution which ought to exist, but perhaps have never yet existed, and we consider laws to be just in proportion as they conform to this ideal. It is the reconciliation between these two views which is the chief problem of political Justice.
On what principles, then, is the ideal to be determined? This is, in fact, the question which has been chiefly in view from the outset of the chapter; but we could not satisfactorily discuss it until we had distinguished the two elements of Justice, as commonly conceived-one conservative of law and custom, and the other tending to reform them. It is on this latter that we shall now concentrate our attention.
When, however, we examine this ideal, as it seems to show itself in the minds of different men in different ages and countries, we observe various forms of it, which it is important to distinguish.
In the first place, it must be noticed that an ideal constitution of society may be conceived and sought with many other ends in view besides the right distribution of good and evil among the individuals that compose it: as (e.g.) with a view to conquest and success in war, or to the development of industry and commerce, or to the highest possible cultivation of the arts and sciences. But any such political ideal as this is beyond the range of our present consideration, as it is not constructed on the basis of our common notion of Justice. Our present question is, Are there any clear principles from which we may work out an ideally just distribution of rights and privileges, burdens and pains, among human beings as such? There is a wide-spread view, that in order to make society just certain Natural Rights should be conceded to all members of the community, and that positive law should at least embody and protect these, whatever other regulations it may contain: but it is difficult to find in Common Sense any definite agreement in the enumeration of these Natural Rights, still less any clear principles from which they can be systematically deduced.