REVIEWS 613'. annum, which must be added to a present pleasure in order to ?nake it just balance a future pleasure' ], then the present value of the pleasure is phR t' (Mathematical Appendix, Note V., Second Edition). Some additional parag?-aphs in the new edition render this theorem ?nm-e easy of reception. The same conclusion as before is reached, but less abruptly. The guide now smooths a winding path, whm'e before the ascent was made by a few footholes, difficult for inexpert. climbers. We confess to having been among those who slipped. There is now a mm'e explicit statement of the assumptions which we make in order to 'get an artificial ?neasu?'e of the rate at which he ?a person] discounts future pleasures.' The first is:' that he expects to be about as rich at the future date as he is now' (Second Edition, p. 179). Attention also is called to the'importance of d?'awing a clear distinction between discounting a future pleasure and discounting the pleasure derived from the future enjoyment of a ceTtain amount of a commodity' (Ibid.). Again, it is to be noted that the theorem ' is so worded as to be applicable to all pleasures, and not u?erely to u?arginal pleasre'es, to which some writers have proposed to li?uit its application' (Ibid., p. 617). These points being home in mind, together with some reservations introduced in the u?athematical note refen'ing to the subject (Appendix, Note V.), it will be found on consideration that the exponential law of hedonic perspective is justified with respect to those pleasures at least of which the external sources are exchangable. We do not understand that the law is predicated of those pleasures which are derived from non-transferable objects; or out of relation to a money-market. As we intm'pret, the 'u?an who builds a house for hindself,' in an important passage of the fifth book (chap. iv. page 1), is not a Robinson Crusoe. That ' the motive force tending to deter hhn from building the house would be his estimate of the aggregate of these efforts [the efforts required for building on any p?'oposed plan], the evil or discomu?odity of each being increased in geometrical proportion (a sort of compound interest), according to the corresponding intewal of waiting,' is theo- retically true of an economic re. me, but not in what may be called unconditioned psychology or pm'e hedonics. The consideration of motives acting at different distances of time leads to the discr?ufination betxx'een Rent and Quasi-rent a distinction whicl? pro'haps will p?'ove as important as the d?scovery of the principle of ?'ent itself. It is now perceived that the?'e is a portion of truth in the contention of the Socialist that the profits of the capitalist have a certain analogy to the rent of the landlord. But he is stopped when he proceeds to draw the corollary that the unearned increment may in both cases with like justice and expediency be appropriated by the community. ' The sudden appropriation of Rents and Quasi-rents by the State xx'ouhl indeed have vm'y similar effects in destroying security and shaking the foundations of society; but, if from the first the State had ?'etained tn?e Rents in its own hands, the vigour of industry and accumulation need not have been i?paired; and nothing at all like this,
