Occurs in a number of variant forms: the face is the index of the mind is among those exemplified below. Cf. [Cicero Orator lx.] ut imago est animi voltus sic indices oculi, the face is a picture of the mind as the eyes are its interpreter; L. vultus est index animi (also oculus animi index), the face (also, eye) is the index of the mind.

The eyes‥are the wyndowes of the mynde, for both ioye & anger‥are seene‥through them.
[1545 T. Phaer Regiment of Life 14]

The affections of the minde declare them selues openlie in the face.
[a 1575 J. Pilkington Nehemiah (1585) i.]

I can refell [refute] that Paradox‥of those, which hold the face to be the Index of the minde.
[1601 Jonson Cynthia's Revels D3^V]

I did not study the Eye that best Index to the mind.
[1781 A. Adams in L. H. Butterfield et al. Adams Family Correspondence (1973) IV. 215]

You have not to learn that the face is the outward index of the mind within.
[1864 Mrs. H. Wood Trevlyn Hold I. i.]

The eye, which is the reflector of the external world, is also the mirror of the soul within.
[1940 G. Seaver Scott of Antarctic ii. 48]

If the old saying, the eyes are the window of the soul, were true then this young girl had misplaced her soul.
[1979 J. Gerson Omega Factor iii.]

If the eyes are the windows to the soul, then the monitor is the window to your system.
[1997 Windows Magazine Feb. 205]

He'd never believed in reading things into people's eyes. All that windows-of-the-soul bullshit.
[2000 J. W. Hall Rough Draft (2001) i. 23]

Related to: appearance, significant

Bibliography of major proverb collections and works cited from modern editions is available here.

The Oxford Dictionary of Proverbs. Copyright © 1982, 1992, 1998, 2003, 2004 by Oxford University Press. All rights reserved.