Protestantism and Catholicism teach that we came into existence, as a being, somewhere between conception and birth. They conclude that our inner being is an invention by God.
In support of this claim they will quote Gen 2:7 _
"And the Lord God formed man of the dust of the ground, and breathed into his nostrils the breath of life; and man became a living soul."
They claim that the word "soul" must mean our inner being. However a look at Gen 19:19-20 brings this into doubt. Here we have Lot being told to flee before the destruction of the whole area and all cities within. Lot says _
"Look now, your servant [me] has found grace in your sight, and you have magnified your mercy, which you have shown to me in saving my life; and I cannot escape to the mountain, in case some evil takes me, and I die: Look now, this city is near for me to flee to, and it is a little one: Oh, let me escape there, (isn't it only a little one?) and my soul shall live."
So lot has been worried that he would be killed if going to the mountain. And requests refuge in a small city so his SOUL shall live. Obviously he's saying his soul includes his body. Therefore the quote in Gen 2:7 can't be used to claim the invention of our inner being, but only the beginning of a living human: One that dies at death.
Also note that Abraham asked Sarah, his wife, to say she was his sister so that he wouldn't be killed when they went to Egypt _
"Say, I pray you, that you are my sister: so that it may be well with me for your sake; and my soul shall live because of you."
This is also pointing out that the soul would die if he were killed. Yet our inner being goes on after death. So only we as a human being have come into existence between conception and birth, not our spirit.
Looking at the Bible, then, what does it say in regard to when we, as an entity, began to exist?
I've not found the Bible giving us an answer on that. But it does state that we existed before coming here. There are several texts that clearly demonstrate that man existed before. So often quoted we see the one in Jeremiah.
"Before I formed you in the belly I knew you, and before you came forth out of the womb I sanctified you, and I ordained you a prophet to the nations." Jer 1:5
Now note that it doesn't say that God knew OF him before he was formed in the belly, but that he KNEW him. He also states that Jeremiah had actually had an ordination before this. And also sanctified. - Hard to ordain a non-existence.
It should be pointed out in looking at this subject that we shouldn't be coming to the subject with the doctrine that we didn't exist before, and then having to show great demonstration that we did. We should be coming to the subject with an open and inquiring mind to find out what the Bible actually teaches concerning this subject: When did we come into existence according to the Bible.
"For whom he did foreknow, he also did predestinate to be conformed to the image of his Son, that he might be the firstborn among many brethren." Rom 8:29
Again here we are informed that God knew people before they were born. Now why bother to say such a thing if we didn't exist then? And note, once more he hasn't stated that he knew of them, but that he knew them.
"And that he might make known the riches of his glory on the vessels of mercy, which he had afore prepared to glory. Even us..." Rom 9:23-24
Here he has stated that before coming here he had in some way PREPARED us for glory. A difficult thing to do if we didn't exist.
But these texts are just the warm-ups. This next statement of the disciples leaves no doubt that they believed in a pre-existence of our spirit. And Christ made no dispute of the doctrine.
"And his disciples asked him, saying, master, who did sin, this man, or his parents, that he was born blind?" John 9:2
How can a man sin before being born, unless he existed before, to sin?
Remember that if you come to this subject looking for endless Biblical evidence to prove a point you will hardly ever find any truth. It isn't a question of whether we can invent some other meaning for a statement. We must examine this from the question of whether the Bible presents that man existed before or was invented at birth. And what support is there for either idea. And in this regard the Bible strongly comes out in favor of our spirits existing before birth.
"In hope of eternal life, which God, that cannot lie, promised before the world began." Titus 1:2
To whom did God promise this eternal life, before the world began? If there was no person who could gain eternal life in existence before the world began, who was he promising it to?
There are other texts which could be used. But these are obvious ones that set forth the truth to anyone who is actually interested in God's opinion, rather than traditions of men.
There are those people who have remembered back to parts of their pre-existence. I have had some experiences of this myself.