 From the Humean epistemic perspective, observational, dispositional, and theoretical predicates are successively more and more problematical in relation to their accessibility via experience. The observational describe observable properties of observable entities; the dispositional, unobservable properties of observable entities; and the theoretical, unobservable properties of unobservable entities. Popper suggested that observational and theoretical properties (gravitational strengths electromagnet fields, and such) are ontologically dispositional, too (Popper 1965: 425). But if universals as properties that can be attributed to any member of any possible world are dispositions and the kind of property dispositions are does not depend upon the ease with which their presence or absence can be ascertained, then nomological subjunctives and counterfactuals—taken as instantiations of lawlike generalizations for specific individuals, places, and times—might be explicable as displays of dispositions and of natural necessities (Fetzer 1981).