First-person thought has been a major topic in contemporary philosophy. The main question is how to characterize the kinds of thought a subject has about herself as herself. Typically, these kinds of thought are expressed in language by use of the first-person pronoun such as in the sentences 'I want a cup of tea' or 'I see a tree over there'. This project aims to work out and defend a novel property theory of first-person thought based on a systematic review of the two most dominating contemporary theories. As a working hypothesis, it is proposed that first-person thought is an attitude best characterised as self-ascription of an indexed structured set of properties. The framework for the assessment of opposing theories and development of our own theory will be a collection of desirable features which have been identified as essential in the recent literature and need to be accommodated by a sound theory of first-person thought. The project will answer three research questions: (1) What are the desirable features of first-person thought? (2) Can these features be accounted for by the most promising current theories? (3) How can these features be accommodated in an enhanced version of the property theory? Accordingly, the project will be split into three parts. The first part of the project will identify the desirable features of first-person thought by illustrating the role they have played in the debate between propositional theories of first-person thought (mainly Perry, 1977, 1979; Kaplan 1989b,a) and property theories of first-person thought (mainly Lewis, 1979; Chisholm, 1976, 1981; Feit, 2008, 2010). We will show that these different approaches share at least five features which are held to be essential for first-person thought. However, they differ in highlighting these features. In the second part we will review two very prominent and promising approaches to the topic. On the one hand, Récanati (2007, 2010, 2012b, 2013a) proposes a Neo-Fregean theory which makes extensive use of the notion of a self-file which is a non-descriptive mode of presentation of the subject. On the other hand, Peacocke (2008, 2010, 2014) argues for a descriptivist Neo-Fregean theory which uses the notion of a first-person concept to account for the features. We will exhibit how these current theories relate to our established framework of evaluation and work out the exact way they can accommodate the desired features. We will argue that neither theory can fully account for all of them in a coherent way. Working out these shortcomings will be a major part of the project. In the third part, we will be developing and discussing the hypothesised enhanced property theory. The main idea is to use the Lewisian framework of the de se and expand it in such a way as to be able to account for all the features of first-person thought. We will show how this novel theory relates to its competitors and how it can respond to objections and challenges springing from the motivations underlying these competing theories. In this way, we can achieve a better understanding of first-person thought.