Here is something regarding Heb. 4:12 I would like for you the reader to theologically ponder...

When we analytically look at this particular Heb. 4:12 Passage we see that the “soul” is distinctive from the “spirit” and that the “joint” is equally distinctive from the “marrow”.  As such, in Heb. 4:12 apostle Paul laid down literal penetration markers (soul-spirit separator and joints separator - the marrow) as to what degree the quick and sharp power of the WORD was capable of piercing into.

Moreover, when looking at the soul-spirit relationship they are revealed to be divided by the greek noun “merismos” (separation – i.e. a separator).

However, when we look at the comparative joint-marrow there is no implied “separator” if we suggest that the “marrow” is defined to be the literal “bone morrow”, and as per this suggested analysis the “marrow (bone)” would then be completely enclosed within the stated “joint (bone)” itself. 

Therefore, by comparative analysis this would then imply that the “spirit” would be completely enclosed by the “soul” – i.e. the figurative circle within the circle.

However, this suggested construct of Heb. 4:12 seems somewhat problematic in regards to apostle Paul’s 2Cor. 6:16, et. al., where he declared that “Ye are the Temple of the Living God...”  Implying that the physical structural Temple of God under the Mosaic Law has now been replaced by the mortal human body as the symbolic Temple of the Living God in respect to the New Covenant of Grace.

Therefore, seeing then that the Temple of God under the Mosaic Law and the Temple of God under the New Covenant of Grace are both “trichotomous” – then by direct comparative analysis the Mosaic Temple of God consisted of the physical structure itself which enclosed the Holy Place then the Veil of Separation and then the Holy of Holies (most Holy Place).

Moreover, if we look at the actual greek text (TR) of 1 Thess. 5:23 we find that the spirit – soul – body are each preceded grammatically by the greek definite article “THE” and separated by the greek conjunction “kai”.  Thus, we have THE spirit and THE soul and THE body.  As such, we have a “trichotomously” designed man.

To this end, 1 Thess. 5:23 and Heb. 4:12 then reveals the literal “markers” that are penetrated by the powerful WORD – hence, Body-Soul-Spirit to the inner most “markers” of the greek "merismos" and "myleos" (separators).

Thus, it is only logical then that there must be some literal entities for the quick and sharp WORD to penetrate.  You cannot plunge a figurative sharp knife into nothingness – there must be a marker(s).

However, the Holy Place and the Holy of Holies which were “separated” by the Veil were LINEAR.

Thus, the Holy of Holies was not completely enclosed by the Holy Place – but as stated they were linear...i.e. NOT a figurative circle within a circle.

To this end, please note that apostle Paul in Heb. 4:12 did not say to the “bone and marrow” but rather to the “joint and morrow”, and as we all know a joint is where two objects (bones) are joined together – just as the comparative soul and spirit are suggested to be joined together – but divided by a “separator”.

Therefore, it can be suggested that the “marrow” (equally defined as the innermost part, etc.) is the “SEPARATOR” (i.e. figurative cartilage) between the joints like the separator of the soul and spirit – but they are LINEAR and not a figurative circle within a circle.

I said all of the above to suggest that the spirit is not completely enclosed and encapsulated by the soul but rather each is independent of the other and divided by an innermost “separator”.  Hence, they are linear.