Before dismissing it out of hand, one needs to understand that questions like this come up pretty regularly on sites like Quora. Clearly there are plenty of people cautiously dipping their toes into the beach ripples of the oceans of philosophy. Maybe it’s existential angst. Maybe it’s the stirrings of that wonderful Human attribute - curiosity. And in this age of knowledge explosion, artificial intelligence, hallucinogenic drugs like LSD, Virtual Reality worlds like Second Life, and fake news, we should hardly be surprised to find plenty of people are wondering about how we can be sure of anything.

So, if serious philosophers like René Descartes gave thought to it, why wouldn’t we? In fact it ties in with the entirely serious epistemological subjects of evidence, proof, and how do we know anything. That’s a topic which takes up serious space within the knowledge banks or ‘mind’ of our Oracle, so it’s fair game for an item in my Blog.

And the short answer to the question is:

We’re not certain, strictly speaking.

If that’s not the answer you were expecting me to give then think about it.

“I think, therefore I am” is a pretty good starting point for this topic.

It is more correctly expanded to something along the lines of,

“I am aware of my thoughts, and therefore something must be thinking for such awareness to be happening.”

That’s hardly as catchy as “I think therefore I am,” let alone “Cogito, ergo sum” though, so we won’t hold René to account for the oversimplification.

Nevertheless, in that expanded form it is precisely accurate and hard to dispute.

However, all it really proves is that something exists to be thinking and being aware of thinking.

It says nothing about “We” plural as postulated in the question, it only talks about “I” singular.

And it in no way proves that I am a being, a Homo sapiens or that I exist as a creature within a “real” universe.

I may just be a virtual reality program running in the mind of God, a dreamer in the dream.

So - no, we are not certain that we exist. Beyond the expanded version of “I think therefore I am,” there isn’t absolute proof of anything. However there is lots and lots of evidence.

For example, a new born baby may exist, but it isn’t thinking “I am aware of thinking and therefore …” because it hasn’t learned enough to think such thoughts yet.

In order to be able to think such thoughts one has to have already experienced a chunk of life to learn language and associate the words with ‘real’ world experiences, and have created some sort of conceptual model of time.

This provides a LOT of supporting evidence for the idea that “I” singular exist. And once you kick me on the shins a few times I will grudgingly admit that “you” singular probably do exist too, so almost certainly “we” plural exist.

And that’s about it. I am not certain that “we” exist, but I am very confident that “we” do, to a level of about 99.99999% confidence.

But certainty is 1, or 100%, and that certain I am not.

Lest any of you till think I am being unreasonably sceptical here to entertain doubt about such an apparently obvious fact, let me add some ideas to give you pause for thought.

1. Suppose the question above was asked on a site such as Quora. (It probably has been). What do I know about you - the questioner, except for a few words of a question on a computer screen? Perhaps a Quora AI bot just creates fictitious personna and dreams up questions. How can I know for certain that this is not the case?

2. Dig deeper into my concerns about evidence, proof, paradox, axiomatic systems, the problems of proving that 2 + 2 = 4, and related epistemological issues. After you have chased your own mental tail through the recesses of your ‘mind’ and my Oracle, you too may not be nearly as certain about the existence of a whole bunch of things that you currently take for granted. We could start with your ‘mind’. Not an easy thing to define, observe, measure, or get one’s head around. Are you sure you have one? How about ‘personality’? Read a book by a psychologist arguing that there really is no such thing. What he really meant was that it’s not a useful term in psychology. His supporting arguments are not easily dismissed. He’s arguing that ‘personality’ is just a meaningless word that can’t be usefully / sensibly defined or measured. There’s a word ‘dragons’ too, but just because we can define it doesn’t mean it’s a real thing. So, are you sure you have a personality? How about a dragon?

Hence part of my .00001% of very reasonable doubt.

As I’ve observed elsewhere, I’m a Christian and a ‘believer’, but I’m also a sceptic with a background in auditing. I know what I believe, how much I believe, and precisely why I believe it.

There’s far too many people, Christians, atheists, and others, who keep asking about things like proof and certainty, because they don’t understand much about any of these things. I’m hoping that this site will give many more people the opportunity to gain some wisdom on these matters.

Hope these thoughts prove helpful.