 So far we have been talking primarily about the role of acquaintance in securing a special kind of knowledge. There is, however, another crucial role acquaintance has been thought to play. For philosophers like Russell, acquaintance secures not only the objects of knowledge but the objects of thought itself; it explains not only how knowledge is possible, but also how thought is possible. This is so not just for a special class of thoughts about experiences or experiential qualities as some hold (see  section 3.2,  on demonstrative and phenomenal concepts), but for thought in general. The idea actually goes back to the empiricists who claimed that all simple ideas have their source in experience. When refined the suggestion probably amounted to the view that all simple ideas are derived from objects or properties with which we are acquainted or of which we are directly aware. On Russell’s version of the view, whenever you form a thought, the components of that thought are items with which you are acquainted: