You can observe a lot just by watching.

-Berra,Yogi Lawrence Peter
Quoted in Colin  Jarman The Guinness Dictionary of Sports Quotations (1990).

You see, but you do not observe.

-Doyle, SirArthur Conan
  The Adventures of Sherlock Holmes,'Scandal in Bohemia'.

   For my part, when I enter most intimately into what I call myself, I always stumble on some particular perception orother, of heat orcold, light or shade, pain or pleasure.I nevercan catch myself at any time without a perception, and never can observe anything but the perception.

-Hume, David
  A  Treatise of Human Nature, bk.1, pt.4, section 6.

For a man to write well, there are required three necessaries: to read the best authors, observe the best speakers, and much exercise of his own style.

-Jonson, Ben
Timber: or Discoveries made upon Men and Matter (published 1640).

   Observe how system into system runs, What other planets circle other suns.

-Pope, Alexander
  An Essay on Man, epistle1, l.25^6.