In Shakespeare's Othello, what does Iago mean when he says "in following him I follow but myself"?

Early in Shakespeare's Othello, Iago,
the villain of the piece, tells one of his dupes, Roderigo, this about Othello: "In
following him, I follow but myself" (1.1.55).  This statement is typical of Iago in many
ways:

• He openly confesses his villainy. Often he
  confesses his evil directly to the audience, but here and in other places he confesses
  his evil both to us and to another character onstage -- a character
  he assumes he can trust because he assumes that that person is either too stupid or too
  self-interested or too vicious himself (or all three) to be botherd by Iago's
  villainy.


• He shows enormous, almost cocky self-confidence
  in stating his motives so blatantly.


• He reveals his
  self-centeredness to another person, and yet that person fails to realize that Iago's
  self-centeredness may boomerang on the person to whom Iago confides. It never seems to
  occur to Roderigo, at least at this point in the play, that Iago might deceive Roderigo
  as well as Othello.


• Statements such as this one
  paradoxically make the term "honest Iago" -- a term used often throughout the play --
  seem ironically appropriate.  Here he is ironically honest about his plans to be
  dishonest.


• This statement, in its highly self-referential
  language, exemplifes the sin of which Iago is chiefly guilty -- the sin from all his
  other sins flow: his pride, his arrogance, his self-centeredness and
  conceit.


• This statement sums up and foreshadows much of
  the rest of the action of the play.  Iago will indeed "follow" Othello in several
  senses, both literally and figuratively, but his chief concern will also be first and
  foremost with and for himself.

Iago is one of
Shakespeare's most memorable villains precisely because he is capable of speaking so
forthrightly about his own lack of forthrightness.  As he says earlier to
Roderigo,

O,
sir, content you.

I follow him [Othello] to serve my turn
upon him.
(1.1.38-39)

Roderigo, of
course, fails to realize how pertinent this statement is to his own relationship with
Iago.