74. To this, the disciple replied, The delusion, Sir, is gone by your grace; but I have doubts about the changeless nature which, you say, pertains to me.(From Upadesa SahasriChap.2:The Knowledge of the Changeless)
Teacher: What doubts?
Disciple: Sound etc., do not exist independently as they are non-conscious. But they come into existence when there arise in the mind modifications resembling sound and so on. It is impossible that these modifications should have an independent existence as they are exclusive of one another as regards their special characteristics (of resembling sound etc.,) and appear to be blue, yellow, etc. (So sound etc., are not the same as mental modifications). It is therefore inferred that these modifications are caused by external objects. So it is proved that modifications resemble sound etc., objects existing externally. Similarly, these different modifications of the mind also are combinations and therefore non-conscious. So, not existing for their own sake they, like sound etc., exist only when known by one different from them. Though the Self is not a combination, It consists of Consciousness and exists for Its own sake; It is the knower of the mental modifications appearing to be blue, yellow and so on. It must, therefore, be of a changeful nature. Hence is the doubt about the changeless nature of the Self.
Here I suppose is a statement of the obvious which like anything in philosophy which is too clear and straightforward has in it the possibility of error. Sounds etc. occur as the result of an interaction between an aware subject and the world. Sankara reminds us elsewhere that we do not perceive perceptions, we perceive objects. That route to idealism which holds that we are immediately aware of our mental states and by inference from those states to an external object which is their cause, is cut off. Perception is clearly distinguished from inference as a valid means of knowledge. Inference is a movement of the mind itself on the basis of some evidence.
The disciple seems to hold to the idea that there is a inner mental subject with special access to inner mental objects, those mental modifications. This ever changing data must be known by a subject which to keep up with them is changing also. The self in its self knowledge is continuously taking the form of the mental modifications and cannot therefore be changeless. This is his dilemma.