What sort of expression is "Peace through Understanding"? It is a theme, a motto, a dedication, a theme statement, a slogan...; but does it have propositional content? Is it a recommendation, a plea, a demand? The plaque refers to man's aspirations for peace through mutual understanding. Is it a hope? It seems to imply that peace can be achieved through understanding, and that this is desirable--both peace, and that it be gained through understanding. It does not imply that the only way to peace is through understanding. Likewise, an advertisement might promise "Financial security through investment in the X fund", without suggesting that this fund is the only way to financial security. On the other hand, the implied claim is not merely that one way to peace among many others is understanding. The aspiration is that understanding will provide the way to peace, given that peace has proved to be so elusive when persued by other means, such as military superiority, empire, mutually assured destruction, diplomacy, international organizations, etc.. This does not mean that diplomacy should be abandoned in favor of understanding, just as the investment advisor might recommend the X fund without suggesting divestment of all other holdings. Although "Peace through Understanding" is not a declarative sentence, and does not state a specific proposition, it could be refuted in various ways. In general, one might find fault with a slogan, "Y through X", by claiming that Y can never be achieved through X, or very improbably can be achieved, or that Y is not worth the striving, or that although X is a reliable method for obtaining Y, it is so difficult or costly as to make the persuit of Y through X impractical. So, let's consider "Peace through Understanding" to be a special sort of promise or hope. It is not merely a personal promise from one person to another. It was adopted by the Fair committee. Adopting a theme or slogan for a public event like a World's Fair is a special way of using language. It invites endorsement, and the organizers hope that the theme will resonate with people who attend. Attendance does not suffice as endorsement, of course, but participation through the presentation of an exhibit at a fair with a stated theme does indicate some degree of agreeement with it--at the very least, no objection. Endorsement of the theme implies some degree of commitment to the following: (1) that peace is a worthy goal; (2) that understanding is a likely means for achieving this goal; and (3) that understanding itself is an intermediate goal that we have reasonable hope to achieve.