Three Dialogues between Hylas and Philonous

Hylas meets Philonous walking in the garden. Hylas mentions to Philonous that he was thinking during the night about an issue, and claims that Philonous is developing a reputation for holding what appears to be a rather extraordinary position, namely that matter does not exist. After Hylas brings this out in the open, he and Philonous hold a debate that begins with the definition and nature of skepticism. Philonous argues that skepticism suggests doubt, a statement with which Hylas agrees, but then asserts that simply because someone holds an opposing view, this cannot be skepticism. Hylas is reluctant to accept this premise, and Philonous begins the real debate on whether or not matter exists outside of the mind that perceives it.

First, Philonous establishes definitions, beginning with what he calls “sensible things,” meaning material objects that can be perceived with the senses. Hylas accepts the definition, and Philonous asks whether sensible things must be perceived immediately (meaning directly), or if these things can be perceived mediately through the intervention of others. Hylas answers that these sensible things must be perceived immediately. Philonous seizes on this assertion and begins to illustrate how it is connected to his views on matter. He discusses the nature of heat. He asks if a fire in and of itself has a component of heat, or if the heat must be felt in order to exist. He describes a person experiencing pain from burning and indicates that the fire itself does not have an innate quality to cause pain; instead, the pain is the reaction of the person who puts their hand in the fire. Hylas accepts the premise to a point, but counters that there are degrees of heat, and that heat is an inherent property of an object such as fire. Philonous discusses the similarity with cold and extreme cold, and then he illustrates a thought experiment. He asks Hylas to imagine a person with one hand that is hot and one that is very cold. The person places both hands in a barrel of lukewarm water. The cold hand will feel relief and perhaps pleasure, while the hot hand will not. In Philonous’s view, the barrel of water does not have an inherent ability to cause pleasure on its own accord. He points out that the water cannot be both warm and cold at the same time. Rather than innate qualities of the water, the terms “hot” and “cold” describe the person’s experience.

Philonous uses the same line of argument as it applies to taste, using the bitterness of wormwood and the sweetness of sugar as examples. The line of argument continues as he discusses sounds and color. Philonous argues that objects do not have an inherent color. In making the argument, he points to the way colors can change appearance depending on perspective. Hylas attempts to refute Philonous. At first, he adamantly opposes the argument, but by degrees, he starts to bend toward his friend’s position.

Hylas leans on the science of optics, claiming that light agitates particles to create color. Philonous once again upends Hylas’s argument pointing out that the science still does not fully explain that color exists without the mind that sees it unless light exists separate from the mind. Hylas objects and reminds Philonous that philosophers claim that colors and subjective states are secondary qualities separate from primary qualities. Hylas identifies these primary qualities as “extension, figure, solidity, gravity, motion, and rest” (23). According to Hylas, philosophers disagree on the nature of secondary qualities, with some arguing along the same lines as Philonous; however, for primary qualities, there is agreement that these “exist really in bodies” (23). Philonous uses the same reasoning to demonstrate the flaw in this line of thinking and returns once again to his general position that even these qualities must be perceived in order to exist. In the case of extension, figure, and motion, Philonous argues that these are still dependent on observation and sensory perception.

Hylas concedes more ground to Philonous, though he still insists that objects exist independently of perception. He says that because he is a rational being, objects must have a substratum. He likewise concedes that the substratum of an object cannot be observable, but that it exists nonetheless. Philonous attacks this line of thought, particularly Hylas’s concession. He questions how the existence of a substratum can be an empirical position, since the substratum cannot be observed. Hylas attempts to justify his position, but once again he concedes to Philonous’s argument. The conversation pivots to the mental conception of objects. Hylas argues that because he can conceive of an object such as a house or a tree, it must exist independently. Philonous presses Hylas here, and Hylas acknowledges that it seems to align with Philonous’s argument that the conceived object still exists within his mind, not independent of it. Hylas infers that the tree exists even if he cannot perceive it immediately. Philonous discounts this, claiming that even mediately the tree cannot be proven to exist. This leads to a discussion on the nature of perception and ideas that centers on the question of whether objects create ideas. Hylas argues in favor of this view. Philonous objects and insists that “archetypes of our ideas, are not perceived by sense” (40) but instead depend on reason or reflection. Philonous clarifies Hylas’s view and suggests that when one sees an object, they form a mental image of that object, almost as a photocopy of sorts. Hylas insists that he can visualize an object in his mind, which he argues is proof that the object exists. Philonous finally gets Hylas to admit that as a result of the conversation he has begun to sense his own growing skepticism. The two agree that they will reconvene the conversation the next day after Hylas has had time to reflect on the content of this first dialogue.