Unity and the many › The argument from unity

At the beginning of VI.9, Plotinus asks us to consider a ship, a house, a chorus, or an animal. Each is what it is through some unity. Breaking a house into stones preserves some of its constituents while destroying the house. A living body's organization also matters to what it is. For Plotinus, unity is therefore more than a convenient label that an observer attaches to otherwise complete things.

The next step is more controversial. A thing that possesses unity need not be unity itself. Soul organizes and animates bodies, but Soul also has different capacities, including reasoning, perception, and desire. Its own unity calls for explanation. Likewise, Intellect contains distinct intelligible objects. Plotinus therefore refuses to identify even this higher principle with absolute unity. VI.9.1–2 moves from things that are unified to a source that does not consist of several elements held together.

The explanation can be reconstructed as a conditional argument. If composites require a principle of unification, and if an ultimate explanation cannot itself depend on further unification, then the ultimate principle must be simple. The important work occurs in those assumptions. The examples show that organization matters, but they do not by themselves establish that every unity requires an immaterial cause, or that all unities depend on the same cause.

A critic could instead explain the unity of different things through their different relations and activities. A ship and a living organism need not owe their integrity to one identical mechanism. A Plotinian reply would distinguish the mechanisms that organize particular things from the deeper question of how any determinate whole is possible. That reply clarifies the question; it does not compel a critic to accept that a separate first principle answers it. The argument remains open to assessment.

The simplicity requirement also raises a question about explanation itself. Suppose we explain how a choir becomes one performance: the singers follow a score, listen to one another, and respond to a conductor. A further explanation could describe the conventions and skills that make those activities possible. None of those explanations needs to identify a single physical object that contains the choir's unity. The relations may do the explanatory work. This is another modern illustration of the critic's alternative.

The Plotinian challenge is that any such account continues to rely on determinate activities and relations. If those already presuppose unity, they cannot explain unity at its most fundamental level. To accept that challenge is to accept a particular demand on explanation: the account must eventually reach something that possesses no unexplained composition. A reader who regards an indefinitely extended network of relations as explanatorily sufficient without an unconditional ground will reject the demand; a reader seeking such a ground may find it compelling. Their disagreement concerns what a completed explanation must provide.

Even if we accept the demand, we have not yet established everything Plotinus says about the Good. An uncomposed ground is not automatically an object of love, a source of value, or something a soul can approach. Those further claims require the discussions of desire, intellect, and contemplation. Separating the steps prevents the opening argument from carrying more weight than it can bear. It also gives a reader a way to disagree precisely: one can grant that organized wholes require explanation while challenging the inference to a unique simple source, or grant that source while questioning the account of human fulfillment.