Inquiring into the distinction between substance and its intrinsic accidents, whether modal or absolute, we have first to remark that all accidents cannot possibly be reduced to relations; for if relation itself is something _extrinsic_ to the things related, it must at least presuppose a real and _intrinsic_ foundation or basis for itself in the things related. Local motion, for instance, is a change in the spatial relations of a body to other bodies. But it cannot be _merely_ this. For if spatial relations are not mere subjective or mental fabrications, if they are in any intelligible sense _real_, then a change in them must involve a change of _something intrinsic_ to the bodies concerned. Now Descartes, in denying the existence of _absolute_ accidents, in reducing all accidents to _modes_ of substances, understood by modes not any _intrinsic_ determinations of substance, but only extrinsic determinations of the latter. All accidents of _material_ substance were for him mere locations, arrangements, dispositions of its extended parts: extension being its essence. Similarly, all accidents of spiritual substance were for him mere modalities and mutual relations of its “thought” or “consciousness”: this latter being for him the essence of spirit. We have here not only the error of identifying or confounding accidents such as thought and extension with their connatural substances, spirit and matter, but also the error of supposing that extrinsic relations and modes of a substance, and changes in these, can be real, without there being in the substances themselves any intrinsic, real, changeable accidents, which would account for the extrinsic relations and their changes. If there are no intrinsic accidents, really affecting and determining substances, and yet really distinct from the latter, then we must admit either that all change is an illusion or else that all change is substantial; and this is the dilemma that really confronts the Cartesian philosophy. 68. MODAL ACCIDENTS AND THE MODAL DISTINCTION.—The real distinction which we claim to exist between a substance and its intrinsic accidents is not the same in all cases: in regard to some accidents, which we have called intrinsic modes of the substance, it is a _minor_ or _modal_ real distinction; in regard to others which we have called absolute accidents, it is a _major_ real distinction (38). Let us first consider the former.