 His point was that even if people do have stronger and weaker preferences, and even if the strengths of their preferences can somehow be measured and made available as a basis for social decisions, nevertheless ordinal information is all that matters because preferences are “interpersonally incomparable”. Intuitively, what this means is that there is no saying how much more strongly someone must prefer one thing to another in order to make up for the fact that someone else’s preference is just the other way around. Arrow saw no reason to provide aggregation procedures with information about the strength of preferences because he thought that they cannot put such information to meaningful use. 