宋榮子Sòngróngzǐ, also known as 宋鈃 Sòngxíng or 宋牼 Sòngkēng, appears in a variety of places (Zhuangzi 1:03 and CTP 33.03, Mengzi CTP 6B24, Xunzi CTP 6.04, 17.17, 18.31-9, and 21.04-5, which unfortunately lack an online translation). He seems to have been a rough contemporary of Zhuangzi's, a pacifist who encouraged people to simplify their lives and avoid conflict by minimizing their desires, particularly desires for things like prestige, wealth, and power. Like Huizi, he may have been an ex-Mohist who retained the Mohist goal of the elimination of war but opted for different methods of achieving it. As with Huizi, Zhuangzi seems to admire him but also have some reservations: "there is still something left unplanted" (1:03). I am uncertain of the degree to which Zhuangzi disagrees with Song Rongzi's goal or the method.
Of 宋榮子Sòngróngzǐ, 1:03 says, "The whole world could praise him and he would not be encouraged. The whole world could condemn him and he would not be upset. He has settled the difference between inner and outer and distinguished the limits of glory and disgrace. Yet he stops there. With regard to the world, he didn't keep score, but there is still something left unplanted."
Of 宋鈃 Sòngxíng, CTP 33.03 says, "By the warmth of affection [he] sought the harmony of joy, and to blend together all within the four seas; and [his] wish was to plant this everywhere as the chief thing to be pursued. [He] endured insult without feeling it a disgrace; [he] sought to save the people from fighting; [he] forbade aggression and sought to hush the weapons of strife, to save their age from war. In this way [he] went everywhere, counselling the high and instructing the low. Though the world might not receive [him], [he] only insisted on [his] object the more strongly, and would not abandon it. (ctext.org/zhuangzi/tian-xia )
Of 宋牼 Sòngkēng, Mengzi 6B24 says, "Song Keng being about to go to Chu, Mencius met him in Shi Qiu. 'Master, where are you going?' asked Mencius. Keng replied, 'I have heard that Qin and Chu are fighting together, and I am going to see the king of Chu and persuade him to cease hostilities. If he shall not be pleased with my advice, I shall go to see the king of Qin, and persuade him in the same way. Of the two kings I shall surely find that I can succeed with one of them.' Mencius said, 'I will not venture to ask about the particulars, but I should like to hear the scope of your plan. What course will you take to try to persuade them?' Keng answered, 'I will tell them how unprofitable their course is to them.' 'Master,' said Mencius, 'your aim is great, but your argument is not good. If you, starting from the point of profit, offer your persuasive counsels to the kings of Qin and Chu, and if those kings are pleased with the consideration of profit so as to stop the movements of their armies, then all belonging to those armies will rejoice in the cessation of war, and find their pleasure in the pursuit of profit. Ministers will serve their sovereign for the profit of which they cherish the thought; sons will serve their fathers, and younger brothers will serve their elder brothers, from the same consideration—and the issue will be, that, abandoning benevolence and righteousness, sovereign and minister, father and son, younger brother and elder, will carry on all their intercourse with this thought of profit cherished in their breasts. But never has there been such a state of society, without ruin being the result of it. If you, starting from the ground of benevolence and righteousness, offer your counsels to the kings of Qin and Chu, and if those kings are pleased with the consideration of benevolence and righteousness so as to stop the operations of their armies, then all belonging to those armies will rejoice in the stopping from war, and find their pleasure in benevolence and righteousness. Ministers will serve their sovereign, cherishing the principles of benevolence and righteousness; sons will serve their fathers, and younger brothers will serve their elder brothers, in the same way—and so, sovereign and minister, father and son, elder brother and younger, abandoning the thought of profit, will cherish the principles of benevolence and righteousness, and carry on all their intercourse upon them. But never has there been such a state of society, without the State where it prevailed rising to the royal sway. Why must you use that word 'profit.'"
Xunzi discusses him in several places. Xunzi CTP 6.04: "Some of these men do not understand the proper scales for unifying the world and establishing states and families. They elevate concrete results and usefulness, and they extol frugality and restraint. But they have disdain for ranks and classes, and so they have never been able to accept distinctions and differences, or to discriminate between lord and minister. Nevertheless, they can cite evidence for maintaining their views, and they achieve a reasoned order in their explanations, so that it is enough to deceive and confuse the foolish masses. Just such men are Mo Di and Song Xing." (Hutton, Xunzi, "Against the Twelve Masters," pp. 43-44.)
Xunzi CTP 17.17: "Songzi saw the value of having few desires, but not the value of having many desires. . . . If there are only few desires and not many desires, the masses cannot be transformed." (Hutton, Xunzi, "Discourse on Heaven," pp. 203-204.)
Xunzi CTP 18.31-9: "‘Master’ Songzi says, “People’s inborn disposition is that they desire little, but they all believe that their inborn disposition is to desire much. This is a mistake.” Thus, he leads about his group of followers, demonstrates his arguments and teachings, and clarifies his terms and analogies, all in order to cause people to understand the sparseness of the desires deriving from their inborn disposition." (Hutton, Xunzi, "Correct Judgments," p. 225.)
Xunzi CTP 21.04-5: "In past times, there were guest-retainers who were fixated—such were the pernicious schools. . . Song Xing was fixated on having few desires and did not understand the value of achieving their objects." (Hutton, Xunzi, "Undoing Fixation," p. 255.)