The current thesis focuses in one of Spain’s most relevant authors: Pedro Dorado Montero. Acting as a bridge between the criminal law conceptions of the 19th and 20th centuries, Dorado Montero offered a very unique, original theory: the ‘Derecho protector de los criminales’ (Protective Law of the Criminals). Towards the end of the 19th century, a clash between the penal neoclassical theories and the new positivist theories took place. As a result, the hegemony of the old school was contested. To this respect, Dorado Montero’s scholarly career, the context in which he lived and the several European and other international influences he received are duly analysed. Therefore, Dorado Montero’s role in the introduction of positivism within Spain and the success experienced by the aforementioned trend are extensively addressed. Furthermore, he was often said to belong to the Spanish ‘correccionalismo’ movement. However, his iusphilosophical and criminal thought seemed to lay closer to positivism than to neoclassical postulates. Even if the debate has been oversimplified in terms of freewill vs. determinism, the approach of this thesis aims at challenging the accuracy of the ‘eclectic’ label which the traditional historiography has attributed to him. On the other hand, a very relevant aspect to focus in is to determine to which extent did Dorado Montero accept positivist postulates as for the rationale of the penalty or as for the determination of the penalty. Spain seemed to accept the positivist rules for the determination of the penalty but it seemed to reject their rationale. Was Dorado Montero partially responsible for the introduction of positivism in Spain? Even if the triumph of positivism as such did not take place in Iberia (at least not completely), the figure of Dorado Montero can offer a valuable insight to this question. The analysis of his positivist ethos could shed some light on the construction of the 20th century penal law and of the criminal law of the future. Dorado Montero was immersed in the world of abstract ideas. Mixing a strong rationalism arising from Kant, and some other German authors, with the advances in criminal anthropology (criminology) and sociology, he described a reality in which every moral value or legal representation was nothing but a mere product of mankind’s imagination. Man is the responsible for the elaboration of morals, law and culture in his own mind. Thus, for him, there were as many moral and legal orders as individuals there were in the planet. Such assertion is polemic even nowadays. Unsurprisingly, the author received criticism from both neoclassical and positivist schools. While the first ones attacked his ‘heavy relativism’, the second ones distrusted his ‘go it alone’ approach. Did this alternative, third way indicate that one should include him within the eclectics? That brings us to the last, concluding remark in which the existence of a so-called ‘Doradian positivism’ is assessed. Despite the interest that such author has grown in the last decades, Dorado Montero is, somehow, left aside. Notwithstanding that, his ‘Derecho protector de los criminales’ is describing the criminal law of the future as well, hugely sieged by the new neurological, medical, psychological and genetic findings of our time.