A social graph may be modeled as a collection of claims. Each claim is associated with an author, an audience, and an assertion about a fact. Probabilistic information may be collected from various sources for a claim, enabling a social networking system to evaluate a truthfulness of the assertion made in the claim. User-declared profile information may be evaluated as claims. A user, entity, or application may make claims about any assertions made in the social networking system. Reputation scores may be determined for users based on evaluations of their historical assertions. Claims may be evaluated for truthfulness using a probabilistic prediction model using heuristics analysis, regression analysis, and machine learning methods. A claims-based profile of users may be provided to viewers based on the contexts in which the claims were made. Viewers may view claims made about users, such as the users' biographical information, contact information, expertise, and interests.