Eighteenth century theories on the correlation of mass and energy included Isaac Newton in 1717, who speculated that light particles and matter particles were interconvertible in "Query 30" of the "Opticks", where he asks: "Are not the gross bodies and light convertible into one another, and may not bodies receive much of their activity from the particles of light which enter their composition?" Swedish scientist and theologian Emanuel Swedenborg, in his "Principia" of 1734 theorized that all matter is ultimately composed of dimensionless points of "pure and total motion". He described this motion as being without force, direction or speed, but having the potential for force, direction and speed everywhere within it.