I am inclined to say that the use of the word 'object' in cases such as 'mental object' is metaphorical at best. I don't think that 'mental objects' exist; use of the term is a way of speaking. But again, 'object' is one of those terms whose meaning seems obvious until you attempt to define it.
As regards the moon (or anything else) existing in the absence of an observer, don't fall into the trap of believing that idealism necessarily implies that things which are not observed do not exist. Moore once remarked that if such idealism were true, the railway carriage would have no wheels when you sat in it. I don't think this is the meaning at all. The point is that reality is perceived by us; from this you might infer that in the absence of perception, it just carries on, an empty earth in an empty sky, or alternatively (and more fantastically), it just ceases to exist. But both those are also a construction, an image in your mind's eye, and from a particular viewpoint, again. Time and space themselves are brought to the picture by the observing agent, and we can never be outside of them to see it from no viewpoint, in no time, and in no location. We can infer this viewpoint, that is all.
So this does not mean that the object
does not exist prior to our perception of it; it means that what we know is our concept of the object. But our concept of the object is not in itself another object; you can't make your consciousness of reality another object in its own right. and form an image of the world 'existing in our minds'. About this point,
W. Teed Rockwell says
Quote:Because Cartesian Materialism says the mind is the brain, it requires us to assume that the only way that the mind can have experience of the world is to somehow get the world inside the brain. Because this is clearly impossible, what with the world being so big and the brain being so small, it is very hard to avoid concluding that knowledge is impossible.
So I do realise that this is a deep philosophical problem. I don't claim to have an answer or a solution, but am challenging the attitude that our 'experience of the world' is the bedrock from which all philosophy must proceed. I think philosophy really starts with an analysis of the nature of the experience of the world, but it is difficult.