Light as Object and Light as Medium

A peculiar, rarely examined, characteristic of Light is that it can be either an object of observation, or a medium of observation.  Now, generally, the former is the topic of interest in Physics.  But, any assumption that the two are equivalent is question-begging, so all propositions hitherto, e. g. regarding its Velocity, pertain only to Light qua object of observation.  Accordingly, Physicists have been unfamiliar with a Kantian argument for the proposition that the Speed of Light is a maximum: The limits of the experience of any object are determined by the Forms of Experience; Light as the medium of any observation is a Form of Observation; thus, nothing observable can surpass the Speed of Light. However, acceptance of this argument depends on the acknowledgement that Physics is Interpretation, not Description, an acknowledgement that has seemingly remained unentertained by Physicists.  Accordingly, implications of the two-fold character of Light have never been considered.