1 Introduction  
2 Galaxies as a Potential Source of the Cosmic Ionizing Emissivity  
2.1 UV-continuum Luminosity Density  
2.2 Evolution of the UV Luminosity Function from Early Times  
2.3 Faint-end Slope and Its Evolution  
2.4 Estimating the Production Rate of Lyman-Continuum Photons  
2.5 Key Uncertainties in Computing the Ionizing Photon Density Contributed by Galaxies  
2.6 The Ionizing Photon Density Produced by Galaxies  
3 Self-Consistent Models of Reionization  
3.1 Standard Reionization Model Using Galaxies  
3.2 Does the Inferred Evolution in the Cosmic Ionizing Emissivity Match that Expected From Galaxies?  
4 Future Prospective