Most likely the number of cells is irrelevant, but there really is no way around the fact that an egg and a sperm are not conscious and that a 5-year old is conscious (for any useful definition of consciousness).

Sure, you could opt for the scientific version of panpsychism, where we attribute a property that we call consciousness purely by analogy to any system with some physical properties. But that still leaves you with the hard work of (a) proving that that property has anything to do with what we normally understand as consciousness (qualia, inner voice, etc.), and (b) defining the point/range where a system has enough panpsychism-consciousness to be considered conscious in the regular sense - e.g. at what size/age does a human have its first experience of thought? When the first neurons differentiate? When it is born? Later? Panpsychism could be a way to give an answer, but you still need to actually quantify this.

Of course, spiritual/religious panpsychism doesn't have this problem, it can posit that the soul should exists even outside of a physical body, that electrons can feel love etc. It is not provably wrong, but it is also outside the realm of what we can scientifically study, at least for now.

You can't assume your conclusion like that.

If you define consciousness as "something a child has that a sperm doesn't have" you are muddled up right at the start -- maybe thumbs are the essence of consciousness.

I'm not defining consciousness like that. I defined consciousness (rather vaguely, but in line with the common usage) as having internal experiences, like an inner voice or qualia. I am then asserting that (disregarding spiritual ideas) it is obvious that sperm cells don't have this kind of consciousness, while 5 year old children do have it (and at least some animals as well!).

My point is that panpsychism seems to me to be using definitions to try to hide away the fact that it can't actually answer the questions of consciousness that we are really interested in any more than brain-based theories can.

If your definition of consciousness is vague, how can it be obvious that X does not conform with it?

What test do you apply?

Since there is no way at the moment to formalize the common sense definition of consciousness, I'll use what I have at the moment.

I can well define "consciousness" formally as anything you like, even as something that vaguely intersects with the common-sense definition, like the information schema people did. But the fact of the matter is that we first have to understand consciousness, the vague common-sense concept, and only after we understand it can we give a precise formal definition that is actually useful.

Otherwise, it would be like defining the mass of an object to be the volume of an object - there is some overlap, and it is a perfectly formally defined, but it's just not the right definition for what you want to explain.

Let me ask you - do you believe that when a photon in the red wavelength hits an electron, the electron "sees red" in the same sense that you "see red" when that same photon hits your retina? What about your retina itself? Does it "see red" in the same sense that you do?

I've read your discussion, and having talked about something related recently, came up with a (IMHO) descent definition:

Consciousness of a physical system A is the difference between the behavior of A and the behavior of a system Aavg, that has the same content as A, but mixed randomly (think water and organics of the right weight and proportion simply mixed in a barrel).

This apparently breaks when you start using tools though.

Im afraid that by this definition, a cell in my body is about as conscious as I am, and the LHC is far more conscious than I am.

Also, this definition does nothing to capture the difference between a philosophical zombie and a human, or help us tell if there is such a difference.

I don't think a cell in your body is as conscious as you are by that definition. You can probably abuse much more energy to get more difference. You have to sum over the entire volume.

As for LHC, it actually needs quite a lot of people to be "conscious". E.g. to be powered and able to operate, so it makes sense, that, as an organization, it is more conscious than you are.

On the philosophical zombie I don't believe there's any difference in consciousness to a human, and the definition matches that idea.

Now I'd challenge anyone to give a better definition in terms of the number of examples contradicting it.

This is an argument from Sorites' paradox and can be used to deny the existence of mountains.

It's not just the number of cells but the layout and connections between them. Imagine if you could feed a tumour everything it needed to live and it would grow to be disgustingly large mass of undifferentiated cells the size of a whale. That thing isn't conscious.