To my knowledge Carl Jung never directly addressed the topic of hoarding. However, the following paragraph (in italics), which I have divided into parts in order to provide commentary, offers some thoughts relevant to the subject. [I suggest that the italicized text be read as a whole first before then going back to re-read the text along with the commentary.]
The personality is seldom, in the beginning, what it will be later on. For this reason the possibility of enlarging it exists, at least during the first half of life. The enlargement may be effected through an accretion from without, by new vital contents finding their way into the personality from outside and being assimilated. In this way a considerable increase of personality may be experienced.
Like the body, the personality is capable of rapid growth during the first twenty years of life. Much of that growth occurs through observation and modeling of others, through formal and informal education. The development of inherent potentials and abilities allows the individual to move through the world in an effective and creative way and establishes a healthy foundation for further personality growth.
We therefore tend to assume that this increase comes only from without, thus justifying the prejudice that one becomes a personality by stuffing into oneself as much as possible from outside.
Due to the nature of our early learning we may view our growth as coming primarily through schooling, books, things we are told and other outer life experiences. We may associate personality growth with the intellect, the acquisition of “facts” and the assimilation of the established, collective worldview.
But the more assiduously we follow this recipe, and the more stubbornly we believe that all increase has to come from without, the greater becomes our inner poverty.
Real growth of the personality involves a reflective, deeper processing of the events and lessons that come your way in life. It means coming to know yourself—both the light and the dark—and by knowing yourself, coming to know the world and other people as they really are, rather than what you project them to be. Your mind may be full of “facts” and your life full of experiences but they all mean very little if you have not gained insight into your own nature and grown in inner consciousness and servanthood through them.
Therefore, if some great idea takes hold of us from outside, we must understand that it takes hold of us only because something in us responds to it and goes out to meet it. Richness of mind consists in mental receptivity, not in the accumulation of possessions. What comes to us from outside, and, for that matter, everything that rises up from within, can only be made our own if we are capable of an inner amplitude equal to that of the incoming content.
A powerful work of art or an inspirational idea may deeply touch and provide an “aha moment” for one individual but be totally missed or unvalued by another. It is one thing to read a book on ethics; it is quite another to actually embody in word and deed an ethical standpoint. To be mentally receptive to an idea or perspective implies a depth of consciousness that can assimilate, take in and actually digest, utilize and build upon the idea or experience presented.
Real increase of personality means consciousness of an enlargement that flows from inner sources. Without psychic depth we can never be adequately related to the magnitude of our object. It has therefore been said quite truly that a man [woman] grows with the greatness of his[her] task. [C.G. Jung, C.W. Vol. 9,I, para. 215]
Recent research on hoarding suggests that people who hoard have a difficult time distinguishing between the relative value of things, so they save everything. Each saved object might sometime come in handy, or might cause regret if given away and later sought. Therefore it is retained. In addition, most people have an intuitive sense that there is something important that they are meant to glean from this life, important lessons or some enlargement of consciousness.
But the struggle or difficulty in determining what is truly valuable implies an equal difficulty in discerning what is really junk and without lasting value. In this respect people who hoard are far from unique. In fact, hoarding is a graphic symptom of a society that is generally confused about what is of real value in life. We are a society that chases after experiences in the hopes that somewhere in all those experiences something valuable will be collected. Unfortunately, we lack the inner depth and consciousness to assign proper value to the events, relationships and opportunities that we encounter. Perhaps, rather than sensationalizing the behavior of people who hoard we should be thanking them for holding up a mirror to our own collective tendency to cram our lives full of ideas, information, activities and experiences that neither enrich or deepen our soul, the latter being the key task that makes life worthwhile and grows the personality.