The three essays that follow take as their point of departure the formulation of grammatical theory presented in such work as JJ Katz and PM Postal, An Integrated Theory of Linguistic Descriptions, 1954, and Chomsky, Aspects of the Theory of Syntax, 1965. For ease of exposition, I refer to this formulation as the" standard theory". The essays deal with problems that arise within this framework, and present a revision of the standard theory to an" extended standard theory"(EST). The status of deep structure is a central concern in all three essays. In the first," Remarks on nominalization", the device of syntactic features is exploited to formulate the" lexicalist hypothesis" with regard to derived nominals, and evidence is presented indicating that this hypothesis is correct and that the properties of these structures can be appropriately expressed only in terms of the abstract concept" deep structure", in the sense of the standard theory and EST. The status of deep structure is discussed again in the third essay, where further evidence is presented leading again to the conclusion that a level of deep structure (in the sense of the standard theory and EST) must be postulated. The second essay is concerned with inadequacies of the standard theory, and a more refined theory of semantic interpretation is proposed, giving EST: the grammatical relations of the deep structure remain fundamental for semantic interpretation, determining what have been called" thematic relations" or" case relations", but other aspects of meaning are determined by surface structure. The third essay develops EST further. Both the second and third essays compare EST with alternatives, in particular with the approach now often called" generative semantics", and present