Here's an exercise: forget, for a moment, about whether you in your precious consciousness are software or not. If you don't feel like software can capture your true nature, who am I to say otherwise. But think of all those other people in your head – your friends, family, loves, acquaintances, role models. People who inhabit your external social world, but you also have little models of them in your head – representations of them, in the most literal sense.
Are these representatives like the symbolic structures, or more like Freudian agencies? Both I suppose. But the latter sounds more basic. We internalize voices of parents, not dead facts about them. But the point is, we know there is something like that, even if we can't agree on the right model for it. Imago is one term for these.
Now, are these models software? I mean, kind of! They are informational structures, they emit language, they judge our actions, we run imaginary conversations with them. Something from the real person has been incorporated into our minds, we've build an image of them, but one that we can use, it's animated and deeply integrated into our mental functioning. Sounds like software to me, or at least, more like software than anything else.
But if these introjected others are software, then so, most likely, is the ego, our model of ourself, which is based on them. We are not just software or just ego of course, we are embodied beings with mental hardware as well – but at some level we are running programs we've picked up from the people and culture around us.
However, that level may be distinct from consciousness, which is more immediate, embodied, and nonrepresentational. That is harder to see in terms of software, although it may be perfectly naturalistic and nonmagical. So I don't want to argue that we are software in toto, just that some aspects of mind might be better understood if we apply software metaphors to them.