Plotinus is not the first philosopher to concern himself with dialectic but he is among the most famous. The Platonist tradition with Socrates and Plato already established two important dialectical conceptions: the conversational dialectic (Socratic dialectic) in which opposing parties (or individuals) discuss a matter and arrive at a conclusion from drawing the contrast between proposition A and proposition B; and the dialectic of ascent-descent (Platonic dialectic) in which the movement upward to light and truth contrasts with the descent downward to darkness and pure matter (which is opposed to ideal-form). Christianity too, in the writings of St. Paul and St. Augustine most prominently, also highlight a certain dialectic of contrasts as well.
The dialectic was already on display in Plotinus in Ennead 1.1 and Ennead 1.2. In discussing life, soul, and self, Plotinus cast the dialectic of ascent and descent as interior in man with consequences to the soul: the good and beautiful soul ascending upward to the intellectual-principle and back to the One or the bad soul descending downward and only being concerned with pure matter and therefore not ascending back to the One. Likewise with the contrast between civic and purificatory virtue being opposites (though in this case civic virtue isn’t wholly bad though does not bring the purification needed to the soul as it lacks intellectualization).
Because our soul is immortal and comes from the all-knowing One, the soul, when placed into a human body (descending away from the One) retains knowledge of the good, true, and beautiful but most be awakened to return to understanding. For Plotinus, the dialectical progression toward Truth follows as such: Impulse, Memory, Knowledge. According to Plotinus, impulse is the madness involved with first encounter – like the musician who encounters beauty for the first time and is driven by impulse to capture it in his work, “he must be led to the Beauty that manifests itself through these forms; he must be shown that what ravished him was no other than the Harmony of the Intellectual world and the Beauty in that sphere, not some one shape of beauty but the All-Beauty, the Absolute Beauty; and the truths of philosophy must be implanted in him to lead him to faith in that which, unknowing it, he possesses within himself. What these truths are we will show later.” It is also important to realize here, as is common in Plotinus, that Beauty is the gateway to Truth, Beauty leads us to Truth and Beauty awakens the soul to the intellectual-principle.
But impulse is not enough and does not come to formalize understanding. Through impulse, however, the dialectic progresses toward memory (or recollection; much like Plato’s theory of recollection). Through moving beyond mere impulse, to memory, Plotinus argues that the rational soul that begins to remember, or have memory, is recalling the Truth of the matter from the One. The encounter with the “Intellectual world” that he spoke of in his rumination on impulse is why memory begins to move us toward a system of science, or knowledge. Recollection of the Truth is what the metaphysicians need to formalize a system of knowledge.
So from impulse to memory to systemized knowledge, Plotinus says, “[T]his Dialectic [is] essential to all the three classes alike.” Within systematic philosophy Plotinus says is method and discipline. In method the metaphysicians establish logical systems of thought to move from encounter in the material world and proceed upward to the world of ideal-form. Through discipline the philosopher is able to be studious and not slip up into mistakes.
Plotinus’s hierarchy is a combination of Plato and Aristotle. While the soul descends from the One in a deductive manner, the way by which we ascend back to the One is an additive manner. Here Plotinus is synthesizing Aristotle: we encounter the lower truths in the material world which allow us to proceed to the higher orders of truth in the realm of Ideal-Form. We do not start with formal knowledge and deduce from there. We start with lack of knowledge and through encounter, memory, and systematic thought, begin to ascend to the true, good, and beautiful in a process of addition.
Furthermore, Plotinus rejects the blank slate because the soul has within it the true ideas but that they are currently “unknown” to us because they have not yet been experienced which awakens the soul and begins the process of recollection (or memory) which is necessary for systematic knowledge. In discussing math, we can understand Plotinus’s view as this: there is order, harmony, and symmetry to the world. This is a priori and always a priori. In other words 2+2 will always equal 4. This is true whether humans exist or not. As we exist we begin to encounter the world of order, harmony, and symmetry and come to understand this and begin to formalize our systems of science (knowledge) to prove these a priori truths.
But in order to derive these systems of knowledge we must first encounter truth in impulse. Through impulse and continual encounter we begin to remember the truth of what we’re encounter. Through heightened recollection we can begin to establish methods by which we systemize knowledge in order to teach. This is what allows us to come to know. Plotinus’s dialectic is an epistemological dialectic and not a historicist dialectic (like in Hegel or Marx). The truths of the world are accessible to all at any point in time because we have rational souls. This does not mean, however, that all will come to know the truth. In fact, few people probably will.
Yet, Plotinus’s dialectic is important for future phenomenologists. What is embedded within Plotinus’s dialectic of impulse-memory-knowledge is rising consciousness. Consciousness, here, is the growing beyond myself to greater awareness and understanding which then situates myself into the web of the whole and of the One (Truth). This is a process. It does not happen over time. We can remember it this way. We progress closer and closer to Truth over time and through experience, trial, and error. This is why Plotinus was, nevertheless, an influence over figures like Hegel, Marx, and Husserl.
What can we summarize from Plotinus’s dialectic? Our soul (rational mind) possesses the truths of the world but is currently in a state of slumber or sleep (non-remembering). Through encounters with Beauty and Truth in the world we are awakened and begin to have heightened awareness of truth. We attempt to capture this beauty and truth in impulse. Through constant encounters and attempts to capture beauty and truth we come to recollect the truths that we already possess in our minds. From this the philosopher is able to establish a systematic method of knowledge. Within this progression to systematic knowledge is growing consciousness within the person, the soul, in which the soul realizes its connectivity to the web of the whole. Lastly, Dialectic is necessary for knowledge. It is a process of growth and accruement, not a single moment revelation.