How can we know that a mind-independent world exists outside of our senses if our senses are subjective? We have first-personal perspectives (FPP) and so, if our first-personal experience is subjective, how can we know that an objective world exists outside of our senses? Well, I have two arguments for the existence of a mind-independent world—what I call “the argument from prediction” and “the argument from causality.”
P1: If there is a physical world independent of human minds, then we can make consistent predictions and perceive it.
P2: We can make consistent predictions about the world and perceive them.
C: So there is a physical world independent of human minds.
P1: If there is causality in the world, then there is a world independent of human minds.
P2: There is causality in the world.
C: Therefore there is a world independent of human minds.
In this article, I will justify each premise of both arguments.
For this article, I will be operating under this definition of mind-independence: X is mind-independent if the existence of X is not dependent on a thinking or perceiving thing. This is a form of metaphysical realism, where there are two theories:
a. that physical objects do not depend for their existence on being perceived or conceived by mind, and
b. that there are physical objects.
The argument from prediction
Premise 1: Only if there were a world independent of our minds could we then make predictions about what occurs in the world. For if what we perceive wasn’t independent of our minds, then we wouldn’t be able to make predictions about the world (ones that turn out to be true, of course). A mind-independent thing is a thing that exists without a thing that thinks and perceives it; so it would exist without an external observer. If humans weren’t here anymore, and if all animals went extinct while the earth was still intact, then the world would still exist.
Premise 2: We constantly make predictions about scientific phenomena, and while of course some of the predictions are wrong, some are right. If some of them are right, then it follows that there is a world out there that’s independent of our minds. A great example is the prediction of Halley’s comet. Edmund Halley—discoverer of the Halley’s comet—observed that 3 comets which appeared in 1531, 1607, and 1682 had similar orbits. He then reasoned that they were the same comet. So using these 3 data points, he stated: “Hence I dare venture to foretell, that it will return again in the year 1758.” Halley didn’t live to see his prediction come to fruition, but 16 years after his death—right on time—the comet appeared and verified his prediction. This is actually a solid example of the fact that we need to make risky, novel predictions, which could falsify a hypothesis in question, but if the observation holds, is evidence for the hypothesis in question. It is, of course, because there is a mind-independent world that Halley’s prediction came to fruition and this prediction best justifies the truth of P2.
Conclusion: Thus, due to considerations that we can make predictions about what occurs in the world, we can then say that there is a mind-independent world. The example of Halley’s comet best illustrates this. It is only due to the fact that we can make consistent predictions about what occurs in the world that we can then successfully conclude that a mind-independent world exists.
Quite obviously, scientific inquiry allows us to generate risky, novel predictions and therefore knowledge, and it does allow for correct predictions about the futures states of the world.
So similar to my argument from prediction is my argument from causality. Predictions are derived from possible causal effects. So, if one has a hunch on a possible arrow of causation and thusly makes a risky, novel prediction based on their hunch, therefore if the prediction comes to fruition then the causal inference may be valid. And since “causal explanations necessarily generate predictions“, thus, the two arguments I’ve mounted are indeed related.
The argument from causality
Premise 1: P1 is simple—if there is causality in the world then there is a mind-independent world. If there were no external observers in the world, there would then still be chains of causation, say the wind knocking a tree over or waves crashing into cliffs taking down chunks of it into the ocean. The world is a physical thing, and cause and effect is related to physical things—the relations between physical things can be predicted and we can then use scientific experiments to show the causal relations between each variable.
Premise 2: This premise is undoubtedly true. For example, if I take a rubber band, place it on my left thumb and pull it back with my right finger and let go of it with my right finger, then it will become a projectile and go in the general area that I aimed at. These considerations are of course one of scientific realism—and the SEP article on scientific realism states that “a general recipe for realism is widely shared: our best scientific theories give true or approximately true descriptions of observable and unobservable aspects of a mind-independent world.” And it is our scientific predictions that use causation as the benchmark which shows that a mind-independent world indeed exists.
Conclusion: So we can then rightly state that due to causality existing in the world, that a mind-independent world does exist. If we did not observe causation, then we could say that there is no mind-independent world.
Reality is clearly mind-independent, based on these two arguments. If it weren’t, then we wouldn’t be able to make successful, novel scientific predictions and there would be no causality in the world. The fact that we use the scientific method to generate novel predictions is tantamount to the claim that there is a mind-independent world. Physical objects exist, and since only the physical is measured, then we can make scientific theories about phenomena and then generate predictions about what we think might occur should certain conditions hold.
The existence of a mind-independent world is put well by Lavazza (2016):
If there were no external reality independent of the knowing mind—a reality that can be investigated insofar as it is accessible by our senses and our tools, predictable in its change and mostly interpretable according to law-like regularities—scientific inquiry would be neither practicable nor would it give us knowledge. And in any case this knowledge would not be effective and practical in the sense of allowing for correct predictions about future states of the world.
Basically, both arguments can be reduced to:
P1: If we generate successful, novel, risky predictions using the scientific method, and if causal explanations necessarily generate predictions, then there is a mind-independent world.
P2: We generate successful, novel risky predictions using the scientific method using causal explanations which necessarily generate predictions.
C: Therefore, there is a mind-independent world.
The three arguments I’ve given are valid, and I have argued for the truth of each premise. So it follows that a mind-independent world does indeed exist.
The whole point of having a brain is to make predictions.
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