The whole argument has problems, but on the one point, (the difference in essence between ideas and material things) the metaphysics are hardly clear.
For instance, I have a coffee cup sitting on my desk. Material thing... has mass and volume. But! The idea of the coffee cup... what I perceive as the coffee cup is a work of interpretation. For example, it has color (in this case black). You and I know that the actual coffee cup has no color. Waves of light bounce off of it at certain wavelengths, and a "mind's eye" interpretation of those wavelengths is displayed before me.
That "mind's eye" interpreted image has no weight, volume etc. The causal aggregate (the actual coffee cup) does. The the idea does not. That's the point Berkeley is trying to make. He goes on to say, we only ever experience ideas so (as far as we're concerned) material things aren't real. But let's not consider all that at the moment. I at least have to agree with him that ideas are essentially different. I disagree with him on the existence of material reality.
For instance, I have a coffee cup sitting on my desk. Material thing... has mass and volume. But! The idea of the coffee cup... what I perceive as the coffee cup is a work of interpretation. For example, it has color (in this case black). You and I know that the actual coffee cup has no color. Waves of light bounce off of it at certain wavelengths, and a "mind's eye" interpretation of those wavelengths is displayed before me.
That "mind's eye" interpreted image has no weight, volume etc. The causal aggregate (the actual coffee cup) does. The the idea does not. That's the point Berkeley is trying to make. He goes on to say, we only ever experience ideas so (as far as we're concerned) material things aren't real. But let's not consider all that at the moment. I at least have to agree with him that ideas are essentially different. I disagree with him on the existence of material reality.
