This chapter argues that sign languages have a crucial role to play in the foundations of semantics, for two reasons. It discusses the cases sign languages provide overt evidence on crucial aspects of the Logical Form of sentences, ones that must be inferred indirectly in spoken language. The chapter also discusses the one dimension, sign languages are strictly more expressive than spoken languages because iconic phenomena can be found at their logical core. A crucial property of sign language anaphora is that loci can be created ‘on the fly’ in many different positions of signing space, and that there is no clear upper bound on the number of loci that can simultaneously be used, besides limitations of performance. The first similarity is that sign language pronouns obey at least some of the syntactic constraints on binding studied in spoken language syntax.