Abstract Grounding necessitarianism (GN) is the view that full grounds necessitate what they ground. Although GN has been rather popular among philosophers, it faces important counterexamples: For instance, A = [Socrates died] fully C [Xanthippe became a widow]. However, fails to C: could have obtained together with B and Xanthippe were never married], without obtaining. In many cases, debate e...

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This paper introduces a -calculus with explicit substitutions, corresponding to an S4 modal logic of constructive necessity. As well as being semantically well motivated, the calculus can be used (a) to develop abstract machines, and (b) as a framework for specifying and analysing computation stages in the context of functional languages. We prove several syntactic properties of this calculus,...

The nuclear fuel cycle can be truly closed by supp lementing today’s thermal reactors with fast reactors, which can use as fuel the heavy, fissionable isotopes that accumulate in thermal-reactor fuel. In a fully closed cycle, the waste for disposal consists only of fission products with trace amounts of actinides. Eliminating the transuranics reduces the heat load in the repository, increasing ...