Wholeness is the most striking feature of the systems at all levels of organization of living matter. It arises and develops as a result of structural differentiation and functional specialization within the given system.
Holism emphasizes the organic or functional relationships between parts and wholes rather than focusing on the parts alone. The determining factors, especially in living nature, are considered to be irreducible wholes. This is often briefly expressed in the statement: the whole is more or greater than the sum of its parts. Here more does not at all refer to any measurable quantity in the observed systems themselves; it refers solely to the necessity for the observer to supplement the sum of the statements that can be made about the separate parts by any such additional statements as will be needed to describe the collective behaviour of the parts, when in an organized group. In carrying out this upgrading process, he is in effect doing no more than restoring information content that has been lost on the way down in the progressive analysis of the unitary universe into abstracted elements.
The holist proceeds from below, trying to retrieve the lost information content by reconstruction, whilst the reductionist procedure (with which it is contrasted) moves from the top down, gaining precision of information about fragments, but losing information content about the larger orders that are left behind.