It is argued that both the resonance peak and low-energy incommensurate res
ponse observed in high-T-c cuprate superconductors have a common magnetic o
rigin. These physical quantities represent universal signatures of an under
lying incommensurate spin state both below and above the superconducting tr
ansition temperature. In this framework the resonance peak is the reflectio
n of commensurate antiferromagnetism. Our theoretical scenario gives an acc
ount of the main universal features observed in various families of superco
nductors and predicts those that have not been observed yet experimentally.
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