The quantity of action is the product of the mass of the bodies times their speed and the distance they travel. When a body is transported from one p… - Pierre-Louis Moreau de Maupertuis

On the 15th of April 1744, I described the principle upon which the following work is based, in the public assembly of the Royal Academy of Sciences of Paris, as reported in the Acts of that academy.
At the end of the same year, Professor Euler published his excellent book Methodus inveniendi lineas curvas maximi minimive proprietate gaudentes. In a supplement to his book, this illustrious geometer showed that, in the trajectory of a particle acted on by a central force, the velocity multiplied by the line element of the trajectory is minimized.
This observation gave me great pleasure, as a beautiful application of my principle to the motion of the planets, which is determined by this principle.
From the same principle, I will now try to derive higher and more important truths.

The first law is the same for both light and material bodies; they both move in a straight line, as long as they are not deflected by an outside force.
The second law is also the same as that governing the reflection of an elastic ball from an impenetrable surface. Mechanics shows that such a ball is reflected from such a surface so that its angle of reflection equals its angle of incidence, as observed for light.
But the third law still requires a plausible explanation. The passage of light from one medium to another exhibits behavior that is totally different from a ball moving through different media.

We cannot doubt that all things are regulated by a supreme Being, who, while he has imprinted on matter forces which show his power, has destined it to execute effects which mark his wisdom... Let us calculate the motion of bodies, but let us also consult the designs of the Intelligence which makes them move.