I'm not at all convinced qualia exist. I think any intelligence would necessarily feel as if it was experiencing qualia.

Let me start by making a distinction: When you take a bite of an apple, you experience a variety of flavours: It's sweet, tart, and has a distinct apple aroma as well. Let's hone in on the last of those. If you took apart an apple under a microscope and examined its flavour compounds, you could find what chemical causes you to experience the sensation of apple flavour, but you would not find apple flavour itself. Let's call the experience of eating an apple and feeling a taste that has its own quality about it which is unique and distinct from every other taste apparent qualia—the conviction that qualia exist and you're experiencing them. The apple flavour itself is an actual quale.

Suppose we build a smart computer, self-aware enough to hold a conversation about philosophy. And let us suppose that we can say for certain that this computer has no access to actual qualia, and we know because we've solved the hard problem of consciousness. Apple flavour is real, we know where to find it (in dimension X or whatever) and only human neurons can access it. This computer does have senses, though, and its senses are abstract. When we look at a stop sign, we don't know which of the millions of rods and cones are firing in our retinas, no more so does our computer know which pixels of its camera are sensing which wavelengths. We, and the computer, just know that we're seeing red. We deal in abstracts.

We put an apple into this computer's mechanical mouth. It chews, it tastes, and we ask it to describe the flavour. "It's sweet, it's tart, and it has a distinct apple aroma," it says. Very well, it doesn't need access to actual qualia to know this. Apples contain sugars, acids, and apple flavour compounds. The computer is just listing the names for the flavours which correspond to those chemicals.

"Computer," we ask, "tell us how you can tell that the apple is apple-flavoured."

"Well," it responds, "the chemical signals from my mouth, as interpreted by the digital plumbing of my mind, are telling me there's an apple flavour."

"Can you describe this flavour to us? Is it the same as strawberry flavour?"

"No, they're different flavours, but I can't really describe them to you. I can just tell they're different."

You take a small white pill and put it in the computer's mouth. "Oh, this is an apple-flavoured pill," it remarks.

"How can you tell it's apple-flavoured?" you ask.

"Well, the flavour is the same as the flavour of an apple."

"Can you describe that flavour?"

"No, it's indescribable. But it is distinct. That's why I can recognize it."

As we go on with our thought experiment, it becomes clear that this computer is experiencing apparent qualia. To the computer, all these flavours are unique and distinct and recognizable—they must be, in order for its senses to function. How can this happen, if it doesn't have access to actual qualia? Well, qualia are the basic building blocks of our senses. They are abstract: The flavour of an apple may be reducible to a set of other flavours, but those base flavour are atomic. You can't break down sweetness any further, or even really describe it at all; it simply is itself.

Any intelligent entity with senses will interpret those senses in terms of basic building blocks. Those basic blocks will be distinct and recognizable; in order to tell the difference between red and yellow, the colour red must exist in the mind in a way which is distinct from the colour yellow. Because these building blocks are atomic, that distinction is irreducible. It is very easy to look at these atomic abstractions and marvel at them, and it's intuitive to start asking questions like, "What is redness itself? What is the source of the actual quale which I am experiencing when I look at something red?", but we're jumping the gun there. Apparent qualia, the experience of unique and essential sensory building blocks, arises necessarily from self-aware examination of sensory input regardless of whether there are any actual qualia or not. If we must necessarily feel that "redness" exists in order for our senses to work, how can we ever be sure that this feeling reflects an actual "redness" and is not just a necessary illusion?

A final argument: We exist because natural selection tweaked the structure of some self-replicating acids over the course of billions of years until they were smart enough to examine the world around them and question their own perceptions of it. The consciousness we exhibit is not essential to this; the only goal of our design is reproduction. Even if you don't think a computer can feel actual qualia, a computer can certainly make decisions to optimize survival and reproduction, which is all we actually need to do. Why would evolution give us access to actual qualia when we don't need them? Why aren't we simply biological computers? As our thought experiment earlier suggests, however, a biological computer would feel as if it had access to actual qualia even if it didn't. Perhaps evolution could construct a complex qualia-sensing interface using science that humanity hasn't even conceived of yet, but it could also construct a simple biological computer that is convinced it feels actual qualia even though it doesn't. Both would work equally well. Even if actual qualia do exist, Occam's razor suggests we don't have access to them.