A great deal of our acquisition of knowledge is dependent upon the assistance of 'external' factors. For example, it can depend on the use of technology (e.g. your iPhone), or on one's social environment (e.g. when one trusts the word of an expert). Nevertheless, it might be held that knowledge is essentially an 'internal' matter. That is, that while one might make use of external resources when acquiring knowledge, such as instruments (the iPhone) or informants (the expert), whether or not one knows is ultimately just down to the individual and their own 'internal' cognitive resources. It is, after all, the individual who is successfully making use of the instrument, and the individual who makes the decision to rely on the information provided by the expert. While such an 'internalist' account of knowledge has for a long time been central to the theory of knowledge, it has come under pressure in recent years, with the pressure coming from several different quarters. Epistemic externalism holds that factors about which one is completely unaware can have a significant bearing on whether one has knowledge. For example, some epistemic externalists have argued that when one acquires knowledge the belief-forming process used (e.g. one's eyesight) must be in fact reliable, whether or not one is aware that this process is reliable. Content externalism holds that environmental factors can have a bearing on the content of one's mental states (i.e., what those mental states are about). For example, some content externalists have argued that whether one's thoughts are about a particular substance in the world, such as water, can depend on facts about the chemical composition of the substance in question. Consequently, on this view whether one has knowledge that a particular substance is water can depend on facts about one's environment. Extended cognition holds that factors which are outside of one's skin can in certain conditions be genuine constituents of one's cognitive processes. So, for example, if an agent and an instrument are related in the right way, then they can potentially form a 'cognitive whole'. Applied to knowledge, extended cognition holds that, say, one's iPhone can in principle be more than just an 'external' instrumental for acquiring knowledge, for it can be a constitutive part of the very cognitive process by which knowledge is acquired. Distributed cognition holds that in certain conditions--such as in the context of a highly collaborative scientific inquiry--we should think of cognition not at the level of the individual but rather at the level of the group. Applied to knowledge, distributed cognition entails that in certain cases we should collectively ascribe knowledge to a group of agents rather than to the individuals who make up this group. All four proposals present a challenge to the 'internalist' conception of knowledge set out above, since in their different ways they undermine the idea that the acquisition of knowledge is primarily due to the 'internal' cognitive resources of the agent concerned. The purpose of this project is to produce, for the very first time, a systematic exploration of these four different ways in which knowledge can be 'externalised'. On the basis of this systematic exploration we will then offer a detailed investigation of two specific ways in which knowledge can be 'extended' that are of particular significance to contemporary cognitive science: extended cognition and distributed cognition. The project will draw together an international body of researchers, both early career and established. It will result in a world-class body of research output which will transform the contemporary research agenda in epistemology and philosophy of cognitive science. It will also engage with the public and with non-academic partners, through public lectures, an 'impact' workshop, and via a dedicated project webpage and blog.