The starting point for this study is the ongoing debate in Poland about courts of justice and judges. The author assumes that it is much better to define the goals of reforming the justice system using universal positive models than incidental negative ones. As an example of such a positive model, the author chose the silhouette of an outstanding English judge from the second half of the eighteenth century – William Murray, Lord Mansfield. Based on the analysis of his body of rulings, he tries to understand Murray’s greatness as a judge. In the last part of the article this is presented based on the most famous ruling of Lord Mansfield – the Somerset v. Stewart judgment from 1772.