AbstractA formal definition ofTLLas a function of M̄nfor polystyrene was prepared with literatureTLLvalues from torsional braid analysis (TBA), differential scanning calorimetry (DSC), and zero‐shear melt viscosity η0. Data from six authors using anionically prepared PS and blends thereof were involved. The resultant linear least‐squares regression line,TLL(°C) = 148.5 − 11.487 × 104M̄ n −1[standard error inTLL(calculated) 4.056 K, correlation coefficientR2= 0.9534] is considered valid from M̄n= 2000 to the entanglement molecular weightMc= 35,000. The “best”TLLvalues reported by Orbon and Plazek from double Arrhenius plots are well below this line for M̄v= 47,000, 16,400, 3400, and above it for M̄v= 1100. These bestTLLvalues are artifacts arising from no or insufficient data points above or belowTLLand/or too many data points nearTg. The associated high enthalpies of activation which they report confirm this diagnosis. The fact that these artificialTLLvalues tend to disappear when checked by the three‐parameter Vogel equation, logη = logA+Bexp[(T−T∞)−1], has no relevance to the controversy concerning the existence and meaning ofTLL. The claim by Orbon and Plazek thatTLLvalues obtained by TBA, DSC, and melt viscosity are all artifacts of the individual methods by which they were obtained is inconsistent with the excellent master plot which they generate. Alternative plotting devices which revealTLL>Tgfrom η0vs.T−1data, as developed by van Krevelen and Hoftyzer and by Utracki and Simha (not previously considered by either party), are reviewed. A statistical examination of the nature of the Vogel–Fulcher–Tammann–Hesse equation, based on synthetic data, is presented. Evidence forTLLin atactic polypropylene is offered based on published data by Plazek and Plazek.TLLis considered to possess both relaxational and q