# The Curious Concept That Almost Nobody Seemed to Care About at First: Virtual Particles in the Post‐War Period

## TL;DR

This paper explores how the concept of virtual particles in quantum field theory became a topic of debate after Richard Feynman introduced his diagrammatic technique.

## Contribution

It highlights the gradual interpretative scrutiny of virtual particles and their connection to broader critiques of quantum electrodynamics.

## Key findings

- Virtual particles gained interpretative attention after Feynman's diagrams popularized them.
- Debates arose not just from their curious characteristics but from critiques of quantum electrodynamics.
- Pre-Feynman developments provided a stronger phenomenological basis for the concept.

## Abstract

Short‐lived, unobservable, and not subject to the usual rules of conservation of energy and momentum, virtual particles—an integral part of the conceptual framework of quantum field theory (QFT)—exhibit a number of curious characteristics which, in recent decades, have in part fueled important discussions about their ontological status. Central to these debates is Richard Feynman's diagrammatic technique for QFT calculations, which provided in the late 1940s the first systematized and generalized description of the concept of virtual particles. At the time, however, the curious characteristics and the ontology of the latter were the subject of little, if any, debate. This article explores how the concept of virtual particles gradually became subject to interpretative scrutiny in the post‐war period. It examines the weight of various aspects of pre‐Feynman developments which once guaranteed a firmer phenomenological anchoring of the scientific practices associated with the virtual particle concept. Subsequently, it shows how the questioning of this concept did not result from a simple assessment of its curious characteristics but was part of a wider critique of the new quantum electrodynamics and Feynman's methods.