In this regard, he has argued in several papers for a detensed theory of time, according to which the present is a merely subjective or indexical notion, on analogy with one's spatial location.

In addition, he has written on the quantum measurement problem, and the implications for it due to, and of it for, the philosophy and science of consciousness.

He has also investigated the problems of localizability in relativistic quantum theories, in collaboration with Gordon Fleming.

More recently, he has appealed to tensor calculus, and its use in much of contemporary physics, to argue against the popular view (propounded by David Lewis) that the world may be described in terms of 'local matters of fact'; i.e. in terms of chiefly intrinsic properties instantiated at spatial or spatio-temporal points.

He has also worked, often in collaboration with research students, on other topics, including: (i) identity and individuation of systems in quantum physics; (ii) dualities especially gauge/gravity duality; (iii) under-determination, and scientific realism, in modern cosmology.