"It was also Hegel who established the view that the different philosophic systems that we find in history are to be comprehended in terms of development and that they are generally one-sided because they owe their origins to a reaction against what has gone before"

The statement acknowledges Hegel's profound influence on how we understand the evolution of philosophy. Hegel did not see past philosophical systems as isolated or static doctrines, but considered them as part of a historical process. For Hegel, the history of philosophy is a dynamic development, where each system arises as a response to the inadequacies of previous ones. The various philosophies throughout history are not simply collections of opinions but manifestations of reason unfolding through time. Each is, in a sense, a necessary stage; it contributes something vital to the ongoing journey of human thought.

Importantly, Hegel maintains that these systems are generally "one-sided". This means that any given philosophical position tends to emphasize one aspect of truth or experience to the exclusion, or neglect, of others. This one-sidedness is not merely a mistake but a consequence of how each system comes about: it arises out of opposition to its predecessor. By reacting against what came before, perhaps by correcting an error, filling a gap, or shifting the focus, it creates a new perspective, but one that is itself limited by its polemical origin.

Walter Kaufmann, by referencing Hegel, urges us to see the development of philosophy as a dialectical process. Each philosophy represents an advance, but also a narrowing, precisely because its advances are shaped by reacting to what it replaces. The philosophical enterprise thus becomes progressive, not in the sense of accumulating truths linearly, but through the dialectical interplay of affirmation and negation, thesis and antithesis, leading to synthesis.

This perspective discourages dismissing past thinkers as simply wrong or outdated. Their systems are moments in a rational development, intelligible and even necessary in context. Understanding them requires seeing not only their content but also the historical and intellectual conditions that shaped their emergence. Philosophic history becomes intelligible as a story of reason in motion, full of tension, opposition, and eventual reconciliation.