Lattice parameter and density data were compiled for Y2O3‐Stabilized ZrO2, both from the literature and from experimental measurements. The data are described very well over a wide range of composition by the model of Aleksandrov et al., which assumes Y substitution for Zr in the unit cell with compensating anion vacancies. Effects are noted in two‐phase cubic‐tetragonal materials which indicate significant lattice strains in the two‐phase materials.

Results are presented for the measured single-crystal elastic constants of yttria-stabilized zirconia, for yttria contents of 1.7 to 20 mol%. The results cover a range of materials which vary from a mixture of monoclinic, tetragonal, and cubic to those which are fully cubic. These single-crystal measurements are used to calculate the bounds on the elastic moduli for polycrystalline materials. Comments are made on the elastic anisotropy of zirconia relative to a number of other single-crystal ceramics, with graphical comparisons of the anisotropy of Young's moduli of these ceramics.

The following propositions seem both plausible in their own right and apparently inconsistent: (1) Moral judgements like 'It is right that I V' ('valuations' for short) express beliefs; in this case, a belief about the rightness of my D-ing. (2) There is some sort of a necessary connection between being in the state thejudgement 'It is right that I ' expresses and having a motivating reason, not necessarily overriding, to (D. (3) Motivating reasons are constituted, inter alia, by desires. The apparent inconsistency can be brought out as follows. From (1), the state expressed by a valuation is a belief, which, from (2), is necessarily connected in some way with having a motivating reason; that is, from (3), with having a desire. So (1), (2) and (3) together entail that there is some sort of necessary connection between distinct existences: a certain kind of belief and a certain kind of desire. But there is no such connection. Believing some state of the world obtains is one thing, what I desire to do in the light of that belief is quite another. Therefore we have to reject at least one of (1), (2) or (3). Call this the 'moral problem', and call those who respond 'revisionists' and 'reconciliationists'.1 Revisionists accept the inconsistency, and so seek to explain away the apparent plausibility of at least one of (1), (2) and (3). Thus, for example, emotivists, prescriptivists and projectivists * The three papers that comprise this symposium come out of very extensive discussion between the three symposiasts-so extensive that sometimes we can no longer tell which ideas began with whom. But as will be plain, we have not ended in full agreement. Besides our indebtedness to one another, we are indebted also to