IGN's Chad Grischow described "Spirit" as the "perfect showcase for fantastic skills", praising her ability to sing both upbeat tracks and "tender piano ballads". Sarah-Louise James from the "Daily Star" gave a positive review, saying, "Fans of her sweet, soaring vocals and power ballads won't be disappointed." Chris Elwell-Sutton of the "Evening Standard" said that "Spirit" will be "a very successful album with some much-needed grit." Digital Spy's Nick Levine gave the album four out of five stars, claiming that although Lewis had a pallet of different producers working with her, they managed to prevent her from sounding "too fusty or old-fashioned." Stephen Thomas Erlewine of Allmusic said "Lewis can hit those big notes but make it seem easy, never straining her voice and building nicely to the climax. Unlike most divas, there is a human quality to her voice, as she's singing to the song, not singing to her voice." He compared it to Mariah Carey's debut album, but criticised the old-fashioned sound. Popjustice's review was brief, summing up that "["Spirit" has four absolutely blinding tracks on it, three far better than average tracks on it, and some others which are quite good. There are no totally chronic songs on "Spirit" apart from 'A Moment Like This'." "The Boston Globe"s Sarah Rodman praised Lewis's ability to make unremarkable songs sound impressive, saying "The tracks are impeccably manicured, super-tuneful, and offer lyrics about the various agonies and ecstasies of love that are unremarkable in and of themselves but reach nuclear-threat levels of desperation thanks to Lewis's voice."