You perceive the object and hence, the object is the cause of your perceiving-the-object; object being perceived by you, becomes the subject or kernel of the event. However, object in this sense is pure abstraction, there is no possible relation to the object as such. Hence, in perceiving the object, what it is is the functioning of perception. It's not that you hear the bell, its the bell-hearing, or the object as adverbial modifier of the functioning-hearing. To make this move from object-centred perception to functioning-centred perception, you take the direction suggested by the 'I', as in 'I am hearing the bell' or 'I am hearing-the-bell.' But you don't take ts path all the way because to do so you would end by wondering how it was that you created or conjured the bell-hearing. So you only go part the way, the 'I' is a signpost, an arrow, and not a place. As the functioning the causal being of the virtual object is simply allowed, without further question. Of course, even the functioning is an abstraction but it is closer to the immediate truth to the direct experience, than the formerly believed-in object.