... causal theories of per-ception with sense-datum theories, when in fact they arequite independent of each other. The criticism, then, is thatcausal theories of perception promote a form of scepticismwhich ... informa-tion has to be gleaned, somehow, from the state of the sys-tem’s sensors, which in the case of the human visual systemare the retinal surfaces of our eyes. At this level of abstrac-tion, ... lower-level repres-entations of information about the state of the system’ssensors are transformed, through the application of mathem-atical algorithms, into higher-level representations of information...