I am ostensibly a "trichotomist"....which is to say, that there are those unique facets of mankind which are not shared by those same animals which posses the "breath of life"....In Genesis 1:20 God speaks of the nephesh or "breath of life" which signifies the being of "higher" animal forms which have what we might call "soul"....but we should note that they were not directly "made" or "created" in the same sense that man was....If we look closely, we see that God said:
Gen 1:20 ¶ And God said, Let the waters bring forth abundantly
and
Gen 1:24 ¶ And God said, Let the earth bring forth the living creature
Not Quite so with man....There IS Something different, and how we describe it will inevitably result in some Philosophical categorization no doubt....but God did do something somewhat different with man....rather than the "waters" or the "Earth" "bringing forth" we see that....
Gen 1:26 ¶ And God said, Let us make man in our image, after our likeness:
Gen 1:27 So God created man in his [own] image,
God "made" the beasts...but God BOTH "made" and "created" man...In his image...the Hebrew terms are different: He both:
Made: `asah
and Created: bara'
Man in his own "image"....
God did not command the "Earth" to "bring him forth" as he did the animals..(although that was the same substance from which he made the animals) see:
Ecc 3:19 For that which befalleth the sons of men befalleth beasts; even one thing befalleth them: as the one dieth, so dieth the other; yea, they have all one breath; so that a man hath no preeminence above a beast: for all [is] vanity.
Ecc 3:20 All go unto one place; all are of the dust, and all turn to dust again.
Ecc 3:21 Who knoweth the spirit of man that goeth upward, and the spirit of the beast that goeth downward to the earth?
So, given our passage in Genesis, and these suggestions in Ecclesiastes, I think we have to come to a delineation between what man SHARES with the beasts and what he possesses UNIQUELY that he does NOT share with them...I suppose I would argue that man has a "Tri-partate form" as does the God-head, and that is what separates (at least in part) man from the animal. In other words...those things which are unique to man, which are not shared by the animals which posses "breath" and "life (as soul)" are what constitutes man's "Spirit" and those things are Eternal.
Animals DO have, what we English-speakers might call "soul" but we also have volition, a sense of aesthetics, moral consciousness, and a desire for Divine Society....unlike the animals. Thus, there are those un-shared facets of mankind which separate him and they are ALL what I would consider to be man's "Spiritual" aspects.....
My dichotomist brethren are indeed correct that the words in Hebrew translated as both "soul" and "spirit" are indeed inter-changeable....but that doesn't mean the concept is....after all, the term "concubine" and "wife" are often the same word but the context supplies a different meaning, as does the terms for "virgin" "young woman" and "Soprano"....same word, yes, but the context supplies a different meaning. So I believe it is with "soul" and "spirit". Hebrew does NOT have two differing words...but English does, and for a reason, I think.