Post-structuralism grew out of structuralism and critiqued its assumption that its system of analysis was essentialist. Post-structuralists believe biases are introduced based on the examiner's conditioning, and there is no truly essential form to cultural products as they are artificially formed. This concept of non-essentialism was expanded on by Foucault, arguing gender and sexuality are contrived formations with no more essential quality. One pivotal moment was Derrida's 1966 lecture critiquing structuralism and laying out principles for a new discourse. Post-structuralism aims to deconstruct ideas of essentialism to allow for more accurate discourse, differing from postmodernism which seeks to identify contemporary periods.