Unknown
Because in the materialistic concept of life we can not see Krishna He most mercifully agrees to appear in the form of the Deity. The Deity IS Krishna, but He manifests Himself in a form that appears to be made from material elements that we can see. So in the temples you will find the form of Krishna appearing to be made from marble or metal but actually it is Krishna standing on the alter and Krishna will reciprocate with us in accordance to our surrender to Him.
