Abstract
Fregeans follow Frege (1892) in accepting informativeness and substitution failure as reliable criteria for the existence of senses as objects of thought. In this paper I show that if we accept this, we must also accept the existence of an infinite hierarchy of senses as objects of thought. This is a bad result since it turns Fregeanism into a doctrine according to which object-related thoughts either have an infinite number of objects as contents or none at all. This shows, against the Fregean, that senses cannot themselves be constituents of thought.