With this new self-conscious focus, the issue of racial purity became increasingly important, for if whites were superior it was important to protect this superiority from contamination. Mulattoes in particular were of much more of a threat than before because of the ease with which many of them could infiltrate the white race. The wide swath of mixed race folk that separated black from white was deemed too permeable to maintain purity. The impetus now was to draw a hard fast line between the races. Under this system, one was either black or white. There is no middle ground. As a consequence, acculturation and acceptance of Christianity was no longer a guarantee of equal or even near equal treatment under the law. Race, not religion, soon became the primary basis of differential treatment.
In order to establish a firm boundary between black and white, the colonial legislators developed a strict interpretation of the doctrine that blacks were natural slaves. They expanded this notion to include the mulatto, who, up to this point had been largely exempt. For colonial America, any degree of black ancestry, no matter how small, made one a “Negro”. The white ancestry of the mulatto was of absolutely no legal consequence. If blacks were natural slaves, so was the mulatto; and any freedom that either had acquired during the American grace was purely an accident; and one which apparently required rectification. Laws began to be passed aimed at depriving free blacks of their remaining rights. Black and mulatto indentured servants had to serve increasingly longer terms so that by the end of the 17th century, servitude had become perpetual for both. Furthermore, the colonial lawmakers were adamant that mulattoes, who comprised the overwhelming majority of the free black population, were to be treated the same as blacks.