Quantum mechanics suggests particles lack defined positions and velocities.

Evidence

The unpredictable, random element comes in only when we try to interpret the wave in terms of the positions and velocities of particles. — Hawking, Stephen, A Brief History of Time, 336

Instead, they had a quantum state, which was a combination of position and velocity. — Hawking, Stephen, A Brief History of Time, 106

Categorization

• corroborated: 3 independent passages support this claim — Hawking, Stephen, A Brief History of Time, 336; Hawking, Stephen, A Brief History of Time, 106
• XREF: connects to: Quantum mechanics is one of science’s most successful theories yet remains profoundly counterintuitive and resists intuitive sense-making. — Quantum Mechanics and the Limits of Human Intuition