AWS Weld definition is discused proposing concepts such as continuity and fittness for porpouse to understand what is and what for is a weld, which is equivalent to express the weld logos. The existence of two kinds to deal with the engineering problems is emphasized: from the art and from the science of the welding. The first step to leave the art said Kelvin to it when it urged to us to measure and to express our ideas quantitatively; the second is to look for the perspective from which the study object appears in its greater simplicity (Willard Gibbs). Actual welding problems demand suitability in conceptual connections among the input variables of the process, microstructural evolution, shapes of beads and service conditions, so that the solution process, before to be an expeditious design of WPSs, turns out to be a development of procedures based on a holistyc paradigm of welding like the proposed one. This paradigm serves to guide the projects of the Welding Group and its validity is confirmed describing two cases of investigation at random selected.