Leonhard Euler phd? "In 1723, received his Master of Philosophy with a dissertation that compared the philosophies of Descartes and Newton. At this time, he was receiving Saturday afternoon lessons from Johann Bernoulli, who quickly discovered his new pupil's incredible talent for mathematics.[5] Euler was at this point studying theology, Greek, and Hebrew at his father's urging, in order to become a pastor, but Bernoulli convinced Paul Euler that Leonhard was destined to become a great mathematician. In 1726, Euler completed a dissertation on the propagation of sound with the title De Sono." - From the English Wikipedia
At what age did Euler got his first PHD? Some sources say that it was the third time Euler promoted in 1726. This is really confusing. 

Euler's De Sono seems to have been written in late 1826 and perhaps Jan of 1827.  He delivered a defense in a public disputation on 18
