In light of recent observations by the Dark Energy Spectroscopic Instrument (DESI), we study evidence for thawing quintessence over a cosmological constant as dark energy, with emphasis on the effect of the choice of priors. Working with a parametrization for the equation of state parameter motivated by the theory, we analyze the DESI baryon acoustic oscillation data jointly with Planck 2018 and $\mathrm{Pantheon}+\text{or}$ Dark Energy Survey supernovae data and find a preference for thawing quintessence compared to a bare cosmological constant only if we use priors which are heavily informed by the data itself. If we extend the priors to physically better-motivated ranges, the evidence for thawing quintessence disappears.

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• Cosmological parameters
• Dark energy
• Evolution of the Universe
• Bayesian methods