Selection from  Divine Love and Wisdom ~ Emanuel Swedenborg
• These three degrees of height 
[natural, spiritual, and celestial] are in every man from birth, and can be opened successively; and, as they are opened, man is in the Lord and the Lord in man.
• That there are three degrees of height in every man, has not until now become  known for the reason that these degrees have not been recognized, and so long as  they remained unnoticed, none but 
continuous degrees could be known; and when  none but continuous degrees are known, it may be supposed that love and wisdom  increase in man only by continuity. But it should be known, that 
in every man  from his birth there are three degrees of height, or discrete degrees, one above  or within another; and that each degree of height, or discrete degree, has also  degrees of breadth, or continuous degrees, according to which it increases by  continuity. For there are degrees of both kinds in things greatest and least of  all things...  for no degree of one kind is  possible without degrees of the other kind.
These three degrees of height are called natural, spiritual, and celestial.
• When man is born he comes first into the natural  degree, and this grows in him, by continuity, according to his knowledges and  the understanding acquired by means of knowledges even to the highest point of  understanding, which is called the rational. 
Yet not by this means is the second  degree opened, which is called the spiritual. That degree is opened by means of  a love of uses in accordance with the things of the understanding, although by a  spiritual love of uses, which is love towards the neighbor. This degree may grow  in like manner by continuous degrees to its height, and it grows by means of  knowledges of truth and good, that is, by spiritual truths. 
Yet even by such  truths the third degree which is called the celestial is not opened; for this  degree is opened by means of the celestial love of use, which is love to the  Lord; and love to the Lord is nothing else than committing to life the precepts  of the Word, the sum of which is to flee from evils because they are hellish and  devilish, and to do good because it is heavenly and Divine. In this manner these  three degrees are successively opened in man.
• So long as man lives in the world he knows nothing of the opening of these  degrees within him, because he is then in the natural degree, which is the  outmost, and from this he then thinks, wills, speaks, and acts; and the  spiritual degree, which is interior, communicates with the natural degree, 
not  by continuity but by correspondences, 
and communication by correspondences is  not sensibly felt. But 
when man puts off the natural degree, which he does at  death, he comes into that degree which has been opened within him in the world;  he in whom the spiritual degree has been opened coming into that degree, and he  within whom the celestial degree has been opened coming into that degree. He who  comes into the spiritual degree after death no longer thinks, wills, speaks, and  acts naturally, but spiritually; and he who comes into the celestial degree  thinks, wills, speaks, and acts according to that degree. And as there can be  communication between the three degrees only by correspondences, the differences  of love, wisdom, and use, as regards these degrees are such as to have no common  ground by means of anything continuous. From all this it is plain that man has  three degrees of height that may be successively opened in him.
• Since there are in man three degrees of love and wisdom, and therefore of use,  it follows that there must be in him three degrees, of will, of understanding,  and of result therefrom, thus of determination to use; for will is the  receptacle of love, understanding the receptacle of wisdom, and result is use  from these. From this it is evident that 
there are in every man a natural, a  spiritual, and a celestial will and understanding, potentially by birth and  actually when they are opened. 
In a word the mind of man, which consists of will  and understanding, is from creation and therefore from birth, of three degrees,  so that man has a natural mind, a spiritual mind, and a celestial mind, and can  thereby be elevated into and possess angelic wisdom while he lives in the world;  but it is only after death, and then only if he becomes an angel, that he enters  into that wisdom, and his speech then becomes ineffable and incomprehensible to  the natural man. I knew a man of moderate learning in the world, whom I saw  after death and spoke with in heaven, and I clearly perceived that he spoke like  an angel, and that the things he said would be inconceivable to the natural man;  and 
for the reason that in the world he had applied the precepts of the Word to  life and had worshiped the Lord, and was therefore raised up by the Lord into  the third degree of love and wisdom. ...
(Divine Love and Wisdom 236-239)