How do we 'know  ' anything?

Only by way of input into that quality within us which is capable of 'knowing  ' - what we often call the 'mind'.

[Is the 'mind' merely another word for the brain? Is the brain the only place within us in which knowing  takes place? Not necessarily. Probably not. Read on.]

How does such input take place?

One way for certain, and the way with which we are most familiar and which operates most often for us - is by way of physical  perception.

What does physical perception consist of?

At base, it is all a matter of touch - physical contact.

Exterior phenomena 'touch' us (make physical contact with us), and, depending on the nature of the particular phenomenon touching us, we perceive that touching by way of one of our physical senses. (And, interestingly enough, all of these physical senses operate only within a limited portion of the full spectrum of the types of phenomena which they perceive).

The most obvious sense of 'touch' is, well, that of touch .

If an exterior phenomenon makes physical contact with our skin, receptors in our skin react to that contact and transmit a message to the brain which interprets that message as 'touch'. (But there is a limitation on this sense - a threshold limitation. If the physical contact is not of sufficient force or energy, the skin receptors won't react to it, no message will be sent to the brain, and we don't 'feel' anything at all.)

And all the rest of our physical senses are basically touch senses as well. They all require physical contact (and they are all limited in their perceptive abilities.)

If the phenomenon contacting us consists of electromagnetic waves (particles?) - within a limited range of frequencies - our eyes react to it and our brain interprets this message as 'light' - We see.

If the phenomenon consists of percussive or concussive waves (particles?) of energy carried by way of the gaseous medium we call air - again within a limited range of frequencies of such energy waves (particles?), our ears react to it and send a message to the brain which interprets this message as 'sound' - We hear it.

If the exterior phenomenon consists of molecules of certain types, perceptors in our mouths and noses react and transmit messages to the brain which interprets these contacts as 'smell' and 'taste.' (And, as we all know - and fortunately - these receptors are limited in the types of molecules to which they will react - otherwise, phewh!).

This is how we perceive the outside world, by way our five physical senses and our brain's interpretation of their messages. Science has been able to reliably tell us this much.

And the three key points here are:

1. Each of our senses is limited in its range - each can only react to a portion of the spectrum of the type of input it is capable of reacting to;

2. All of our physical senses together are limited in their total range - there are many other types of exterior phenomena to which none of our senses react at all. We have no physical sense by which we can specifically perceive our coming into contact with magnetic fields, bombardment by sub-atomic particles, brain wave emanations from others (and who knows what other types of phenomena of which we are totally unaware even exist because we have no physical sense by which to even perceive them).

3. Each of our brains interpret  the inputs they receive by way of our senses, and do so in a particular way.
(If our brains interpreted differently than they do, we might just as easily 'hear' light and 'smell' sound).

So, there it is. This is the manner by which we come to possess whatever knowledge we may have about the nature of the exterior reality in which our bodies exist.

(Please note that so far we have discussed only the reality exterior to our bodies - beyond and outside our skin. The processes by which we perceive the nature of and goings-on within our skin is something else yet again. Our ability to perceive this inner reality is even more limited than that for perceiving exterior reality, and even less well understood in science. We'll leave it for others to delve into this murky subject with respect to our discussion here.)

This is how we perceive our exterior physical reality, and the only way we do (or can). Whatever we might know about such reality is the result of these processes, and no other.

And one final point needs to be recognized in this regard.

All of our recent technological developments haven't changed this fundamental fact. Telescopes, microscopes, x-rays, radar and the myriad of other instruments we now have are wonderful things. They have significantly enhanced and improved upon the levels, quantities and quality of phenomena we can perceive. But what they have not done (and cannot do) is by-pass the processes just discussed. Whatever amplified views of reality they may provide, those views must still enter into our minds by way of our physical senses perceiving them and our brains interpreting the input of those senses.

So, no matter how we cut it or say it, our knowledge of physical reality exterior to our bodies is, in fact, and to a very large extent, unique to each of us. We are each isolated in a physical body, which attains knowledge of its exterior reality by way of these sensory processes which are very limited. And the inputs of these sense are interpreted by our individual brains. Thus, our awareness (knowledge) of that exterior reality is, necessarily, not only severely limited, but not exactly the same for any two of us.

Does all this at least give us some clue as to the inherent limitations on our ability to KNOW exterior reality by way of our physical senses? I think so.

Yet, this is the arena in which anything which can honestly call itself science must operate. By definition, it can operate in no other. (If it does, it isn't truly science).

So, does this not also at least give us some clue as to the limitations of science?

There are simply many things we can not KNOW scientifically.

Whatever knowledge we might have about those things which are beyond the limits of the abilities of science, that knowledge cannot be honestly called scientific. It must be some other type of knowledge.

Are there other types of knowledge - ways of knowing ?

Of course there are. And we all KNOW that.

We all have inputs into our awarenesses that come in by ways other than by way of our physical senses. Insight. Intuition. Inspiration. (Hallucination?).

The results in our minds of such inputs may be murky and muddled and confusing and even downright deceptive. But they are there, aren't they! (But then again, the results of our brain's interpretation of the inputs from our physical senses can be equally confusing and deceptive, can't they? Optical illusions; Mistaking cold for heat; Sounds and voices which aren't there.).