'I am', 'I am that' and 'I am that I am' are three expressions that originated in religions and from there found their way into esoteric philosophies.1 Here we shall try to trace them, or their counterparts, in a few chosen academic philosophies.
Let us start with the philosophy of René Descartes (1596-1650). Descartes is given a pivotal role in the development of academic philosophy, for he is thought to stand at the root of the turn from Christian philosophy to the modern philosophy of the enlightenment.2 In his central work Discours de la Méthode [Discourse on the Method] he decides to methodologically doubt everything until he stumbles upon an unshakable certainty that cannot be doubted.3 After done away with all doubtable things such as God and mathematics he finds this certainty in himself as a thinking subject. He can doubt everything, but he cannot doubt that he doubts. "I think, hence I am" Descartes concludes.4 The 'I am' is for Descartes thus the basis on which reality is built.
Something similar is initially going on in the philosophy of Martin Heidegger (1889-1976). In Sein und Zeit [Being and Time] Heidegger in a sense starts his philosophical journey by raising the question of the meaning of being.5 And for gaining access to that meaning he sets off in the aforementioned work with an analysis of the being to whom being has meaning, being man.6 This being, man, Heidegger unconventionally calls in German "Dasein".7 'Dasein' basically means 'existence' or 'presence' in German.8 It is made up of the words 'Da', meaning 'there',9 and 'Sein', meaning 'being'10. So compositionally 'Dasein' means basically 'there-being', or in English perhaps rather 'being-there'.
Heidegger names man (the 'subject' in philosophical terms)11 'Dasein', 'being-there', because he looks upon him as always being 'there', meaning 'in the world'.12 When inauthentic the being-there is with the separate beings in the world and when authentic he is with the beings as a whole or with the world as such.13 Thereby the inauthentic being with the separate beings in the world corresponds to a "Was-sein", or a 'being-what', and the authentic being with the world as such to a "Daẞ-sein", or a 'being-that'.14
Now in Heidegger's thought authenticity lies at the root of the veiling inauthenticity, and the being-that thus lies at the root of the veiling being-what.15 So the being-there, the Dasein, may authentically also be named the 'being-that'. This becomes even more interesting when we consider that the being-there, man, whom we just mentioned to be the 'being-that', always understands his own being according to his understanding of the world. When he views the world in an inauthentic way then he himself is inauthentic and when he views the world in an authentic way then he himself is authentic.16, 17, 18 So basically in Heidegger's philosophy the 'Dasein', the 'being-there', the 'being-that', regards the 'I am that'!
Above Desartes' thesis of the subjective 'I am' was considered. And Heidegger's notion of the 'I am that' as the 'Dasein' then can be considered as its antithesis, for therein the 'I am' is found objectified in the world. When these two then are taken together into a synthesis the 'I am that I am' appears. In following this process we have basically completed a dialectic process as it is found in the philosophy of Georg Hegel (1770-1831). For the philosophy of Hegel basically is constituted of such, ever recurring, dialectic processes. The first moment therein always regards the thesis, the given under consideration placed 'on itself' or 'an sich'. The second moment then regards the antithesis, the given placed 'before itself' or 'für sich'. And the third moment then regards the synthesis, the given placed 'on and before itself' or 'an und für sich'. But this synthesis is at the same time also again a new thesis, placed on a higher level so to speak, giving rise to another antithesis and synthesis, and so on.19
In his work Phänomenologie des Geistes [The Phenomenology of Spirit] for instance the 'I am' can very well be taken to correspond with 'the subjective spirit' ['der subjektive Geist'], for the subjective spirit regards the inner man as an individual.20 The 'I am that' then corresponds well with 'the objective spirit' ['der objektive Geist'], for the objective spirit regards basically the outer society of men.21 The 'I am that I am' then corresponds with 'the absolute spirit' ['der absolute Geist'], where in society's religion and philosophy contemplation on man's absoluteness takes place.22
Thus we see how the expressions 'I am', 'I am that' and 'I am that I am' or counterparts thereof occur in some of the academic philosophies.