Metamorphosis

Marx uses the term metamorphosis, for example in relation to the exchange of commodities for money in order to emphasise that both sides of this exchange have an inner connectedness.  It is not two totally distinct things that simply exchange places, but a process by which one becomes the other and vice versa.

The butterfly has an innner connectedness with the caterpillar.  It does not simply take the place of the caterpillar but emerges from it.  The commodity can only be exchanged for money because both have an inner connectedness, both are expressions of Exchange Value and of Use Value, but each only has the form of one of these at any one time.  It is for that reason that both contain the other within it, just as the butterfly contains the caterpillar within it, that enables one to become the other.

The commodity is Exchange Value for its owner, but Use Value for its potential buyer.  Likewise, Money is Exchange Value for its owner but Use Value for the seller who obtains it in exchange for their commodity (its usefulness is that it can be used to purchase other commodities).  In the process of exchange one metamorphoses into the other.

This concept of metamorphosis is not restricted to the exchange of commodities.  Dialectics takes as its starting point the nature of reality as based on continuous change.  Change as a continuous process itself involves the idea that the present is pregnant with the future i.e. the future is not some discrete period of time that simply takes the place of the present,  but is itself inextricably bound up and connected to the present.  The future emerges out of the present.