Kelsen's time at Heidelberg was of lasting importance to him in that he began to solidify his position of the identity of law and state from the initial steps he observed as being taken by Jellinek. Kelsen's historical reality was to be surrounded by the dualistic theories of law and state prevailing in his time. The major question for Jellinek and Kelsen, as stated by Baume is, "How can the independence of the state in a dualist perspective be reconciled with its status (as) representative of the legal order? For dualistic theorists there remains an alternative to monistic doctrines: the theory of the self-limitation of the state. Georg Jellinek is an eminent representative of this theory, which allows one to avoid reducing the state to a legal entity, and also to explain the positive relationship between law and state. The self-limitation of the sphere of the state presupposes that the state, as a sovereign power, by the limits that it imposes on itself, becomes a rule-of-law state." For Kelsen, this was appropriate for as far as it went yet it still remained a dualistic doctrine and therefore Kelsen rejected it stating: "The problem of the so-called auto-obligation of the State is one of those pseudo-problems that result from the erroneous dualism of State and law. This dualism is, in turn, due to a fallacy of which we meet numerous examples in the history of all fields of human thought. Our desire for the intuitive representation of abstractions leads us to personify the unity of a system, and then to hypostasize the personification. What originally was only a way of representing the unity of a system of objects becomes a new object, existing in its own right." Kelsen was joined in this critique by the distinguished French jurist Léon Duguit, who wrote in 1911: "Self-limitation theory (vis Jellinek) contains some real sleight of hand. Voluntary subordination is not subordination. The state is not really limited by the law if the state alone can introduce and write this law, and if it can at any time make any changes that it wants to make in it. This kind of foundation of public law is clearly extremely fragile." As a result, Kelsen solidified his position endorsing the doctrine of the identity of law and state.