Things have no intrinsic entity because they arise dependent on causes and are interrelated.A simple illustration:
What we know as a 'bed' comes from the collection of numerous components to assume a known form. A 'bed' other than these components does not exist. When all the components are dismantled, no 'bed' remains. All that is left is the concept of 'bed.' Even that concept is without independent existence, but must relate to other concepts, such as 'sleeping,' a plane surface, a base, an empty space and so on.
Concepts are formed in the mind through the association of relationships. For most people, once a set of relationships is formed into a concept, the habit of clinging to things through craving (tanha) and clinging (upadana) attaches to those concepts as fixed entities. Such clinging isolates the concept from its relationship with other things, and stains perceptions with notions of 'me' and 'mine,' leading to identification with them and thus preventing any true understanding.
Things have no root cause or first arising. Tracing back along the stream of causes ad infinitum, no root cause can be found for anything. Yet there is a tendency for people to try to find some kind of original cause; this kind of thinking conflicts with the way of nature and causes perceptions which are at variance with the truth. It is a form of self-deception, caused by the human habit of stopping any inquiry into causes at the immediate one and going no further. Thus the usual understanding of cause and effect, believing in an original cause for things, is inaccurate and contrary to the laws of nature. Considering how things are, it is necessary to search further back by asking,
"What is the cause of that so-called Original Cause?" and so on. None can be found. The question should rather be asked,
"Why should things have a root cause anyway?"