The Buddhist Heart Sutra says - form is emptiness, emptiness is form. It goes on to reiterate and emphasize this - form itself IS emptiness, emptiness itself IS form. It doesn't say we have emptiness then later we have some form created independently. It says that the two are the same - identical in essence.
We certainly shouldn't take that on as a new belief or replace our existing beliefs with this new "spiritual" one. We should investigate why they say this - what do they mean by this? We usually do one of two things - we either take on these statements as truth without investigating, or we immediately discard them because they don't jive with our existing beliefs.
Emptiness is the absence of any content - an empty room has nothing in it. But the emptiness spoken of here is emptiness beyond even the space - beyond even the idea of a room to hold the emptiness. Emptiness in this context is absolute - so much so that we cannot conceive of it - to conceive of it requires some sort of boundary, some edges - something by which to describe it. Emptiness evades even the most critical attempt to describe. It isn't dark because emptiness goes beyond darkness and lightness yet contains both. It isn't vast or deep because emptiness goes beyond vastness or depth while containing both. Depth requires something to measure against - emptiness is void of any content which could be used to measure depth. It isn't space because space is only space when measured against form - emptiness is beyond both form and space yet contains both.
What we CAN describe is FORM. Form is, of course, any "thing" we can know - this cup is form, this desk is form, that cloud is form. What the Heart Sutra is saying is that there is emptiness - this indescribable essence - and form - exactly the same "thing" as emptiness. Because we can describe form, we see it come and we see it go, we discard emptiness and equate existence with the coming and going of form. We literally give each "thing" or form an existence of its own. It is built into our language and the very context of experience.
I am looking at a rock. That rock "exists". By that we mean - when rock was formed, its existence began. When rock ends, its existence will end. That is difficult to conceive because the rock goes on a long time. But what about this pencil? When pencil was formed, did a new existence begin? Certainly we say "pencil exists!" - It does "exist" but does it have a new, separate, independent existence? The pencil is part wood and part lead (and maybe rubber and metal). Did the wood exist prior to pencil? Did the lead exist prior to pencil?
So "pencil" doesn't really "exist" in an absolute sense - it is wood and lead, which already existed prior to the formation of pencil. And wood is a tree - tree was there - lead was there somewhere. Did tree pop into existence from nothing? Tree was a seed - before it was a seed it was an acorn maybe - acorn was a blossom from another tree, which was in turn a seed of another tree. Lead was various atomic particles coming together under pressure - those atomic particles were already there prior to the pressure - the result of which was "lead" - which later was used in the pencil.
We can dissect any "thing" in the exact same way. A little of this is enough to really make us see that no "thing" has an absolute, independent existence. No "thing" stands alone in existence. WHAT that "thing" is was already there - yet we say "pencil exists" - with that we MEAN that pencil has its own existence. We think of all "things" this way. And that is our error.
With that error, we take the form-ation of this embryo as the creation of a new existence. Yet the embryo has a similar history. The embryo was the combination of the cell of the mother and the cell of the father. Both cells merged and began to grow, to duplicate - that growth resulted in an organism of considerable intelligence. We say that this is a person - someone who will be "born" - an existence which stands alone - apart - an existence which wasn't there before, which is here now, and which will later end. Existence will end. Of course the organism is there where it wasn't before, but is there truly a new, independent EXISTENCE in it? Does existence end with the ending of that organism, or only a change in the form, a change of the collection of particles we call "body"?
We can either discard this or consider it. If you get what's being referred to, there will be a little a-ha and an attempt to dive deeper into this investigation, along this line of inquiry. If we really do want to get to the bottom of WHAT we are, we may take this and run with it - tracing back any "thing" to see if we can actually find where existence began anew with the beginning of the form.
If we do so, we may discover that our idea of transient existence is false - that we have given fleeting existence to fleeting form - we have taken existence as something which comes and goes in each form.
If we do so, we may come to realize that this pure "existence" is itself emptiness - void of everything yet the very essence of any "thing" - any "form". In this we may discover the Heart Sutra, not as a nice little spiritual poem but a clear pointing to reality.
And in this, we may discover that WHAT we are isn't a little independent, temporary thing but the very Heart of all "things".