# Outline of a Logic of Knowledge-by-acquaintance Iaquinto **Opening (not a real abstract):** of knowledge (see, e.g., Bengson and Moffett 2012, Fantl 2016, Ichikawa and Steup 2017). Speaking roughly, these are (i) cases of knowledge in which a cognitive agent S knows that something is true – for example, that the Earth revolves around the Sun, (ii) cases in which S knows how to do something – for example, how to ride a bicycle, and (iii) cases in which S knows a given thing – for example, a given person. For the present purposes, we focus on the first kind of knowledge – the so-called knowledge-that – and the third one – which we are going to call knowledge-by-acquaintance.1 We assume that statements like ‘Mary knows Smith’ are ascriptions of knowledge-by-acquaintance (acquaintance ascriptions for short), just as statements like ‘Mary knows that the Earth revolves around the Sun’ are ascriptions of knowledgethat. Starting from Hintikka’s (1962) seminal work, over the few last decades a