In Types of People, Sarati asked "What's a Maystadt bond, or Rusakov particle pattern?", and it seemed worth starting another thread to discuss particle philosophy in more detail.

Rusakov particles are elementary particles that seem to be attracted to thoughts and to each other. Souls are primarily composed of Rusakov particles, and the patterns their fields cause in the flows of nearby particles are quite distinctive. The patterns around intelligently crafted objects or well-used tools are very different, because they are basically reactive residue from interactions, without active fields of their own.

"Maystadt bond" is just the name for the particular kind of energetic field that exists between a person and their soul, which causes Rusakov particles to travel in loops between them.