Thermoplastic dual core having positive hardness gradient inner and outer core layers

A golf ball comprising:

• an inner core layer comprising a first thermoplastic highly-neutralized ionomer comprising a copolymer of ethylene and an α,β-unsaturated carboxylic acid, an organic acid or salt thereof, and sufficient cation source to neutralize the acid groups of the copolymer by 80% or greater, and having a geometric center hardness and a surface hardness greater than the geometric hardness to define a first hardness positive gradient having a first slope, S1;
• an outer core layer disposed about the inner core, the outer core comprising a second thermoplastic highly-neutralized ionomer comprising a copolymer of ethylene and an α,β-unsaturated carboxylic acid, an organic acid or salt thereof, and sufficient cation source to neutralize the acid groups of the copolymer by 80% or greater, and having an interior hardness and an outer surface hardness greater than the interior hardness to define a second positive hardness gradient having a second slope, S2;
• and
• an outer cover layer.