“I told about the whole being greater than the sum of its parts. “It's that way with people, too,” he said, “only with people it's sometimes that the whole is less than the sum of the parts.””

Source: Principles of Gestalt Psychology, 1935, p. 176
Context: Even these humble objects reveal that our reality is not a mere collocation of elemental facts, but consists of units in which no part exists by itself, where each part points beyond itself and implies a larger whole. Facts and significance cease to be two concepts belonging to different realms, since a fact is always a fact in an intrinsically coherent whole. We could solve no problem of organization by solving it for each point separately, one after the other; the solution had to come for the whole. Thus we see how the problem of significance is closely bound up with the problem of the relation between the whole and its parts. It has been said: The whole is more than the sum of its parts. It is more correct to say that the whole is something else than the sum of its parts, because summing is a meaningless procedure, whereas the whole-part relationship is meaningful.

It loses its essential properties when it is taken apart. The elements of a system may themselves be systems, and every system may be part of a larger system.
Ackoff (1973) "Science in the Systems Age: beyond IE, OR and MS." in: Operations Research Vol 21, pp. 664.
1970s

Source: The Alphabet of Grace

Holism and Evolution (1926)

The Hindu, "Strengthening Indianness ", Sunday, Jan 19, 2003, Available Online http://www.hinduonnet.com/thehindu/mag/2003/01/19/stories/2003011900240300.htm
2000s

Source: 1920s, Kritische Theorie der Formbildung (1928, 1933), p. 305; as cited in: Cliff Hooker ed. (2011) Philosophy of Complex Systems. p. 189

Poems (1869), A Strip of Blue (1870)
Context: A part is greater than the whole;
By hints are mysteries told.
The fringes of eternity, —
God's sweeping garment-fold,
In that bright shred of glittering sea,
I reach out for and hold.

Source: Flipped

Source: Sociology and modern systems theory (1967), p. 42.