This text examines the problem of individuation, framing it fundamentally as a problem of integration. Rather than following the ancient atomist tradition that views the individual as the smallest indivisible particle, the author defines an individual as a complex structure that maintains its unity despite its internal diversity. The essence of an individual lies in its capacity to remain a unified whole; any division that destroys this unity effectively liquidates the individual itself. The author introduces the concept of the "concretum" (from the Latin concrescere, to grow together) to describe how multiplicity becomes a singular entity. Consequently, the "principium individuationis" is reinterpreted as a "principium integrationis" or unity within and from multiplicity. Crucially, this integration must be an organic, internal process of "growing together" rather than an external arrangement or construction. While external factors can stimulate or support this growth, the formative power of individuation remains an internal property that cannot be planned or engineered from the outside.