Laplace (1749 - 1827)

"An intelligence knowing, at a given instant of time, all forces acting in nature, as well as the momentary position of all things of which the universe consists, would be able to comprehend the motion of largest bodies of the world and those of the lightest atoms in one single formula, provided his intellect were sufficiently powerful to subject all data to analysis; to him nothing would be uncertain, both past and future would be present in his eyes"  -
Quoted  in "The Origins and Growth of Physical Science", Vol 2, Hurd and Kipling (ed), p. 319.

More  Laplace

The above statement was made based on the success of classical mechanics in understanding terrestrial and celestial phenomena at that time.

We now know that, in practice, the above assertion may fail even in 'classical' systems due to even minute errors that may be present in the initial data - chaos theory.