Proclus broadly uses the terms "universal" and "particular" as well as "whole" and "part" almost interchangeably, without making a clear distinction based on their fundamental meanings. "Universal" (καθόλου) and "particular" (κατὰ μέρος) are derived from "whole" (ὅλον) and "part," (μέρος) but they are used independently of those terms in meaning. The meanings of "whole" and "part" are quite obvious and well-defined: a "whole" is something composed of parts, while a "part" is something that, when combined with other parts, forms a whole.

The terms "universal" and "particular," however, have two different common meanings. In the first sense, "universal" refers to a term or concept like "human" that can be applied to more than one individual, as opposed to a "particular" which applies only to a single individual, such as "Socrates." In the second sense, "universal" is a broader concept that includes other concepts, and, conversely, "particular" is a narrower concept within "universal." For example, "animal" is a universal with respect to "human," and "human" is a particular within the broader concept of "animal."

Initially, it might seem that there is no direct connection or correlation between "whole" and "part" and "universal" and "particular" in any of the meanings mentioned above. However, there may be some relationship between them. Generally, it is believed that "universal" and "particular" relate to concepts, while "whole" and "part" pertain to physical objects. Today, we often use "universal" and "particular" to compare two concepts and in relation to their instances. Among these two, a "universal" is a term that applies to all instances of a concept, whereas a "particular" applies only to some instances of that concept.

For example, "animal" is a universal, and "human" is a particular, since "animal" applies to all instances of "human," but "human" does not apply to all instances of "animal." Nonetheless, the relationship between instances of "human" and "animal" is one of whole and part, because a collection of animals forms a whole that is larger than and includes the collection of humans. In other words, the set of humans is a part of the broader set of animals, which, combined with other species, makes up the entire collection of animals. Based on this, perhaps, in the next stage, the relationship between "animal" and "human" could be viewed purely as whole and part, disregarding their instances — meaning that "animal" could be considered a whole, with "human" and other species as parts within it.

It’s important to note that this is, in fact, a kind of analogy; the relationship between concepts is not literally one of part and whole. It’s possible that the reason behind the names "universal" and "particular" and their derivation from "whole" and "part" is precisely this — i.e., the idea that a concept containing other concepts has been likened to a whole, with those concepts as its parts, thus earning the names.

It seems that Proclus also regards "whole" and "universal" as nearly synonymous and often uses the term "wholeness" (ὁλότης) to refer to both meanings. He employs these terms in relation to principles and forms. He considers principles to be universal and particular because, at their core, these principles are a series of concepts with varying degrees of universality, where each level is more universal than the lower level and more particular than the higher level. For example, "unit" is a more universal concept than "being," and "being" is more universal than "life." Conversely, "life" is particular relative to "being," and "being" is particular relative to "unit."

He also views each of these concepts as a whole composed of parts, considering them as whole or parts in relation to each other. For instance, "being" already includes "life" and "intellect," and can be seen as a whole constructed from these parts. For this reason, even when "life" and " intellect" appear as independent principles at lower levels, it can still be said that "being" is a whole relative to them, and they are parts relative to "being."

On the other hand, Proclus considers these concepts as a hierarchy of causes, where each level is the cause of the lower levels and the effect of the higher levels. In this view, all four terms are generalized to causes, which are also called whole and universal, as well as parts and particulars. Although these terms are originally characteristics of concepts, applying them to natural or metaphysical causes seems unwarranted.

Thus, each cause is considered universal relative to its subsequent causes—its effects—and particular relative to its higher causes—its own causes. As a result of this generalization, each cause is a whole composed of parts, which are, in fact, its effects.