age of twenty-four (he means: twenty-seven), but few possess the versatile genius of Sir William Petty." Knox also makes a comparison with the tractate Of Education of John Milton, published 1644, and thinks that the Advice to Hartlib is "full of original matter worthy of detailed study". References Bibliography (reprint 1921). in two volumes. External links The Advice to Hartlib in Wikisource. Transcribed text in The Hartlib Papers Books by William Petty Philosophy of education 1647 books