Stumbling around in Kant's dark room.
Left and right are not something 'subjective' for which the subject has a feeling; they are directions of one's directedness into a world that is ready-to-hand already. 'By the mere feeling of a difference between my two sides' I could never find my way about in a world. The subject with a 'mere feeling' of this difference is a construct posited in disregard of the state that is truly constitutive for any subject-namely, that whenever Dasein has such a 'mere feeling', it is in a world already and must be in it to be able to orient itself at all. This becomes plain from the example with which Kant tries to clarify the phenomenon of orientation.
Suppose I step into a room which is familiar to me but dark, and which has been rearranged [umgeraumt] during my absence so that everything which used to be at my right is now at my left. If I am to orient myself the 'mere feeling of the difference' between my two sides will be of no help at all as long as I fail to apprehend some definite object 'whose position', as Kant remarks casually, 'I have in mind'. But what does this signify except that whenever this happens I necessarily orient myself both in and from my being already alongside a world which is 'familiar'? The equipment-context of a world must have been presented to Dasein. That I am already in a world is no less constitutive for the possibility of orientation than is the feeling for right and left. While this state of Dasein's Being is an obvious one, we are not thereby justified in suppressing the ontologically constitutive role which it plays. Even Kant does not suppress it, any more than any other Interpretation of Dasein. Yet the fact that this is a state of which we constantly make use, does not exempt us from providing a suitable ontological explication, but rather demands one.