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My senses fool me - How could the senses be self-evident?

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On 7/31/2017 at 2:38 PM, DonAthos said:

My senses do not "tell me" that the sun revolves around the earth, though they do provide the material by which I may come to that conclusion. If this conclusion is in error, then it will also be my senses which provide the material by which I can come to recognize and rectify it.


On 8/1/2017 at 4:15 AM, SpookyKitty said:

No, they won't be. Sense data cannot contradict itself.


No, it can't contradict itself, but our perceptions can appear to.


What do we mean when we say that a pencil out of water looks straight? That there is some *thing* with certain sensible properties (one of which being that it basically looks like a straight line). When we put it in water our sense of sight reports a change in that trait (it's bent) which our sense of touch contradicts. It can't be straight and bent at the same time; that's a contradiction, which is what makes it confusing to perceive. By observing, recording and analyzing how this phenomenon effected a wide variety of things the ancient Greeks conceived of the fact that water bends light (and even measured the precise angle of its refraction).

The *thing* never contradicted itself (that can never happen). Our senses never misbehaved; they showed us the *thing's* every observable attribute, right down to the refraction of its image. Our perception might've appeared to misbehave while integrating a contradiction (sensing both the attributes of straight and bent) but only until we conceived of such a thing as light; that it's what makes our eyes work and also that it can bend. That conceptual knowledge, which was gained by inducing from a large body of observations, resolved any apparent contradiction. And there is no such thing as a non-sensory observation.


The Greek discovery which solved that riddle was based on what they'd seen - with their senses. Galileo realized that the Earth orbits the sun with his telescope and a detailed record of planetary movements (among other things) - and his senses. Einstein formulated his Theory of Relativity in order to resolve some seemingly self-contradictory experiments, which were done with complex, high-tech equipment - the results of which were grasped by the scientists' own senses.

The senses provide the only material available for us to correct any misinterpretation of them.


Now, if you wanted to discuss hallucinations, that'd be a bit more in-depth (optical illusions are a toy case, really) but the fundamental principle wouldn't change:

If you see a giant purple elephant fall out of the sky while tripping on acid but also see a crowd of people beneath it who haven't noticed anything, see that it doesn't cast a shadow as it falls and feel the ground stay perfectly still when it hits, you'll infer that it wasn't real - because of your other sensory material.

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On 8/20/2017 at 11:11 PM, KevinD said:

Skeptic: My senses deceive me and cannot be trusted. This stick appears bent in water, but in reality it is straight.

Objectivist: How do you know that the stick is not actually bent?

Skeptic: [Pulls stick out of water] LOOK!

That is a great explanation but I think one has to go one step further and spell it out.

In both cases, stick in the water and out of the water, the senses are what is being relied upon. One can't say the senses fool me and yet determine the truth using the senses.

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