Space-time: Arena or Reality?

The concept of fundamental particle has been quite elusive along the history of physics. The term fundamental is commonly used as a synonymous of structureless particles. However, this assumption is clearly contradictory. For example, it is impossible to explain spin without assuming a structure for the particle. In fact, a point particle is by definition spherically symmetric, a symmetry violated by the presence of spin. This problem is usually circumvented by saying that spin is a purely quantum property, which cannot be explained by classical physics. This means to keep it as a mysterious property of nature.