of Bacon's 'Advancement of Learning,' which should be a treatise on 'Nature free,' or on arts and manufactures relieved of restraint, in contrast with a 'History of Nature vexed and disturbed,' or of trade under the restraints of the then existing commercial system. Ergastula Literaria The literary work-houses, or 'Ergastula Literaria', which are proposed by Petty in his Advice to Hartlib have become a symbol for the spirit of educational renewal in the seventeenth century. Together with his 'Gymnasium Mechanicum', his 'Noscomium Academicum' and the 'Theatrum Botanicum' they can be found in different studies on the history of education throughout the following ages. The phrase 'Ergastula Literaria' is meant "to cover a whole theory of Education, and that a revolutionary one." Petty "anticipates Pestalozzi and Froebel when he insists that instruction must follow the lines indicated by the child's natural propensities for learning, that the child is essentially an active creature, who learns best by doing, and that he must be taught in reference to his powers and needs of the moment, and not by ways which respect his future only." Critical reception The only work in which Petty wrote extensively about education has acquired quite some attention in scholarly circles. His concept of the Ergastula Literaria is often mentioned. , in his Sir William Petty: A Study in English Economic Literature (1894) gives a rather extensive description of the Advice to Hartlib, naming it "the Tractate on Education". He considers the work, in its "youthful performance", as a demonstration of Petty's "cast of mind", showing the strength and weakness of his character. He writes among other things about the difference between the visions of Milton and Petty on educational reform. , professor of Education in the University of London, mentions Petty as one of the "Pioneers of Modern Education" of the seventeenth century. Anderson gives much attention to the "universal schools" that Petty wanted to establish, the "Ergastula Literaria", "a phrase which is meant to cover a whole theory of Education, and that a revolutionary one." According to , professor of Education at Queen's University Belfast, who wrote an essay about The Advice to Hartlib in 1953 the work was difficult to find for a long period, until it was republished in 1876, and again in 1946. Knox starts his essay with the following statement: "To few it is given to write an enduring treatise on education at the