Isaac Todhunter was born on November 23, 1820 in Rye, Sussex, England, the son of a minister. He attended University College London, where he received the BA degree in 1842 and the MA degrees in 1844. One of his teachers was August De Morgan. Todhunter then taught mathematics at St John's College, Cambridge. He was known for his simple lifestyle and his studious, scholarly manner.
Todhunter was best known during his time for his popular textbooks, including Analytical Statics (1853), Plane Coordinate Geometry (1855), Examples of Analytic Geometry in Three Dimensions (1858), Theory of Equations (1861), The Elements of Euclid (1862), Mechanics for Beginners (1867), and Mensuration for Beginners (1869).
To students or probability, Todhunter is best known today for his A History of the Mathematical Theory of Probability from the Time of Pascal to that of Laplace, first published in 1865. This book remains one of the most widely read works on the early history of probability.
Todhunter was elected a Fellow of the Royal Society in 1862, and was a founding member of the London Mathematical Society in 1865. He died on March 1, 1884 in Cambridge, England