A chemical model that stresses the role of proton donors in soil genesis is proposed. The model proposes that the abundance, strength, and ability of the conjugate bases to participate in chemical reactions are keys to weathering and pedogenic processes. The study of soil solution has been instrumental in determining the role of proton donors and has led to the development of this chemical model. Conventional pedological investigations only analyze the solid phase and consequently do not allow the identification of the proton donors. Soil-forming processes are defined as a combination of weathering and transportational processes occurring in the absence or presence of living and dead biota. Proton donors initiate weathering reactions and participate in transport of ions released during weathering. While the concept of proton and ligand-promoted dissolution is not new, our recent work with solutions collected from different ecosystems has revealed which acids are important in different soils and throughout the horizons in a given profile. The perspective here illustrates the role of proton donors by describing models of soil genesis.In surveying the proton donors present in the soil, it is recognized that not only is the strength of the acid as indicated by the pKaimportant in weathering reactions but also the ability of the conjugate base to form complexes. On this basis, the acids are classified as weak, strong, and complexing acids. Reactions involving these acids are presented indicating their tendency to cause congruent and incongruent dissolution. The influence of the soil-forming factors (climate, biota, parent material, topography, and time) on the source and distribution of proton donors is presented. Finally, three case studies are presented to reveal how studies involving soil solutions have been used to identify the major proton donors and to determine the present soil-forming processes.