The second fundamental assumption and objectivism

To move beyond solipsism we need to make an additional assumption: that an objective reality exists beyond or outside ourself.

Oxford dictionary:
objective, a thing or class of things external to or independent of the mind;
real, having an objective existence; actually existing as a thing;
reality, real existence; what is real; the aggregate of real things or existences; that which underlies and is the truth of appearances or phenomena.
As an individual we cannot know that the sensory information we perceive is generated artificially or originates from a real world. Any belief that it arises from a real world outside us is actually an assumption. It seems more beneficial to assume that an objective reality exists than to live with solipsism, and so people are quite happy to make this assumption. In fact we made this assumption unconsciously when we began to learn about the world as infants. The world outside ourselves appears to respond in ways which are consistent with it being real.

The movie "The Matrix" directed by Larry and Andy Wachowski plays on the idea that sensory information may have an alternate source. The movie imagines that some time in the future humans are held captive and fed sensory information via cables connected to their nervous system. This information creates a realistic world in the minds of the humans. The captive humans think they are moving about in space, talking and so on, but actually their bodies are immobile. It illustrates the vulnerability of our dependence on sensory information albeit using fiction.

Moreover, the functioning of our brains is readily influenced by external agents such as chemicals and physical manipulations. Drugs of various kinds, including alcohol, valium and so on, can alter our perception of our world. Physically probing certain parts of the brain in surgery can induce the perception of light, for example. Brain tumours can induce strange sound and visual sensations. Our belief that an objective reality is the origin of our sensory information rests on the assumption that there is no such interference taking place.

Everything we know, or believe to know about the objective reality rests on this assumption. We can never know that the world is real; the best we can do is assume that it is so. In making this assumptions we arrive at the point of view of objectivism, the belief in an objective reality beyond or outside our mind.

Oxford dictionary:
objectivism, the quality or character of being objective; the tendency to lay stress on what is external to or independent of the mind.

The status of the assumption of the existence an objective reality is also revealed by considering its contrary. If there is no objective reality we can never progress beyond solipsism: all sensations and feelings have no external meaning and other people don't exist. The assumption of objectivism is essential is we are to attach the contemporary meanings to our sensations and feelings and make more sense of them.