Bertrand Russell famously distinguished between 'knowledge by acquaintance' and 'knowledge by description'. For much of the latter half of the twentieth century, many philosophers viewed the notion of acquaintance with suspicion, associating it with Russellian ideas that they would wish to reject. However in the past decade or two the concept has undergone a striking revival in mainstream 'analytic' philosophy—acquaintance is, it seems, respectable again. This volume showcases the great variety of topics in philosophy of mind, epistemology, and philosophy of language for which philosophers are currently employing the notion of acquaintance. It is the first collection of new essays devoted to the topic of acquaintance, featuring chapters from many of the world's leading experts in this area. Opening with an extensive introductory essay, which provides some historical background and summarizes the main debates and issues concerning acquaintance, the remaining thirteen contributions are grouped thematically into four sections: phenomenal consciousness, perceptual experience, reference, and epistemology.