 In IIp40s2, Spinoza discusses four kinds of knowledge or modes of cognition. These are I) knowledge from singular things; II) knowledge from signs; III) knowledge from common notions; and IV) intuitive knowledge. The first two are prone to falsity, as they generate inadequate ideas. Cognition of kind (I) arises from objects represented “through the senses in a way that is mutilated, confused, and without order for the intellect”. This is perception from “experientia vaga”, vague or random experience. Knowledge of kind (II) arises from hearsay, arising “from the fact that having heard or read certain words, we recollect things, and form certain ideas of them … through which we imagine them.” Spinoza groups (I) and (II) together as knowledge of the first kind: opinion or imagination. Inadequate and confused ideas pertain to knowledge of the first kind, and so it is the sole cause of falsity. Both of the sorts of knowledge of the first kind depend upon what we would ordinarily call sense experience. Spinoza does not go so far as to assert explicitly that no true knowledge can ever arise from sense experience. It is only when the senses present us with representations in a way that is “mutilated, confused and without order for the intellect” (IIp40s2), i.e., random, that our resulting conceptions are inadequate. But the question is whether there is any other way, on Spinoza's views about sense perception, that the senses can represent objects to us. Knowledge of the third kind, intuitive knowledge, does not appear to involve the senses at all. It is knowledge proceeding “from an adequate idea of the formal essence of certain attributes of God to the adequate knowledge of the essence of things” (IIp40s2). This knowledge, then, arises from the intellectual consideration of the essence of an attribute itself, rather than from sensuous commerce with modes of that attribute. Knowledge of the second kind, reason, seems a more plausible candidate for arising from experience. This is based on the so-called “common notions”. Common notions are conceptions of things “which are common to all, and which are equally in the part as in the whole” IIp38. Such conceptions can only be adequate, and this would guarantee that the knowledge arising from such conceptions is true. Spinoza also allows that if there were something common and peculiar to the human body and external bodies by which it is affected, and equally in the part as in the whole of each, then the human mind will conceive that thing adequately. The problem, however, is that given Spinoza's views about sensation is it hard to see how such common notions could arise from sensation, and to the extent we can make sense of this, the common notions seem limited to ideas of extremely general features of physical objects, far too general to be a source of any of the kinds of particular observational knowledge required for experimental practice. The inadequacy of a conception of a thing results from its not reflecting the entire nature of a thing's causes. Knowledge of effects is by knowledge of causes, and while things can interact causally only insofar as they share something in common, there can be aspects of the causes of things not reflected in their effects. However, if a conception is of something common to an object and all other things, then there can be nothing in any of its causes not reflected in the conception of it itself; whatever is present in the cause will be present in it as well, hence reflected in the idea of it. But what, we may ask, is even possibly shared by each thing and equally in the part of each as in the whole? The only obvious candidates are properties that, as Schliesser (2017, p. 15) puts it, “reflect the peculiar modal qualities of … a mode”: in the case of extended modes, those sorts of properties that follow from the nature of extension: e.g., motion and rest, taking up space, being subject to motion and to the laws of geometry, etc.. But the sorts of observational knowledge that are crucial to experimental method in science are hardly exhausted by the knowledge that pertains to bodies as such. Indeed, experimental observation depends precisely on the observational knowledge of differences, rather than similarities.