The third premise by Huemer investigates the authenticity of our faculties in relationship to our perspective of the external world. Mike Huemer observes that our insight into the external world gives off an impression that we are reliant on our senses. A skeptic would espouse Huemer’s point and then will try to show that there is no way in trusting our sense organs to flawlessly depict our world to us as it is. First, the skeptic argues that what we obtain from our perceptions are not explicit images of the external word, but simply sense data. For example, you do not actually see a piece of paper in front of you, but a mental image of the paper itself.
Huemer also notes that you cannot have knowledge of an external world unless direct realism or indirect realism is true. Direct realism is the idea that are sense organs can grant us explicit access to external objects and indirect realism is the concept that uses the senses to detect objects internally, opposite of what exists in nature (Brown, 349). However, both concepts are false. Thus, in Huemer’s case the third argument is the strongest argument because it provides us insights into the differentiation of what we actually see and our experience through mental images. Huemer’s theory of the third argument agrees with the skeptic in that no objects divides into two separate things and thus no physical object exists in the external world. We would know the external world exists, if our sense data induces material objects. Therefore, we are not conscious that our sense data is induced by objects and consequently there is no existence of knowledge in the external world.
In the Brain in the Vat argument, Pollock theorizes that our experience through our senses is the only way we have access to the external world. In the story, the guy had his brain removed thus his images were screwed because he could not reprocess former objects in time. His brain is attached to a computer program that can ultimately create experiences of the external world. The skeptic would note that we cannot be sure that we are actually brain in the vat or that our beliefs about the world are totally false. In terms of perception the brain in the vat argument was defended using a conclusion: I think the sky is blue, no brain in a vat can think the sky is blue, thus individuals are not brains programmed.