Krishna said to Karna that by sastras he is Kanina putra and hence morally son of Pandu and can inherit the throne.
The sastras actually does not say it. It was Krishna’s half-truth.
Karna was the Kanina son of Pandu but he is not the son of Pandu and neither was he a Kuru heir. This is as per the same Sastras which Karna also cites as his reason for not joining with Pandavas.
Bhishma mentioned in Chapter 49 of Anushasana parva, what are sons and what are heirs.
- The son of one’s loins is regarded as one’s own self.
- The son that is begotten upon one’s wife by a person whom one has invited for the task, is called Niruktaja. (Aka Pandavas, Svetaketu)
- The son that is begotten upon one’s wife by somebody without one’s permission, is Prasritaja. (e.g. Iravan, Galava Babhruvya, Kamsa)
- The son begotten upon his own wife by a person fallen away from his status is called Patitaja. (Eklavya, Kichaka)
- There are two other sons, viz., the son given, and the son made. (example Kripa)
- There is another called Adhyudha.
- The son born of a maiden in her father’s house and raised there is called Kanina.
- Besides these, there are six kinds of sons called Apadhwansaja and six others that are Apasadas.
These are the several kinds of sons mentioned in the scriptures.
Yudhishthira said, “Some say that one’s son is he that is born in one’s soil. Some, on the other hand, say that one’s son is he who has been begotten from one’s seed. Are both these kinds of sons equal? Who, again, is the son to be? Do thou tell me this, O grandsire!”
Bhishma said, “His is the son from whose seed he has sprung. If, however, the owner of the seed abandons the son born of it, such a son then becomes his upon whose spouse he has been begotten. The same rule applies to the son called Adhyudha. He belongs to the person from whose seed he has taken his birth. If, however, the owner of the seed abandons him, he becomes the son of the person who raised him. Know that even this is what the law declares.”
Well one can argue that Surya never abandoned the son so he is never Pandu’s (Same can be said of Pandavas especially Arjuna whose father was present and active). Pandu abandoned Karna so Karna is not his son. (of course Pandu never knew of him, so Kunti acting on her future husband’s behalf abandons him. Same arguments apply for Veda Vyasa).
Yudhishthira said, “We know that the son becomes his from whose seed he has taken birth. Whence does the husband of the woman that brings forth the son derive his right to the latter? Similarly, the son called Adhyudha should be known to be the son of him from whose seed he has sprung. How can they be sons of others by reasons of the engagement about owning and rearing them having been broken?”
Bhishma said, “He who having begotten a son of his own loins, abandons him for some reason or other, cannot be regarded as the sire of such a son, for vital seed only cannot create son-ship. Such a son must be held to belong to the person who owns the soil. When a man, desiring to have a son, weds a girl quick with child, the son born of his spouse must belong to him, for it is the fruit of his own soil. The person from whose vital seed the son has sprung can have no right to such a son.’ (Surya and Indra have no rights to their sons).
As regards the son made, he is sometimes regarded as the child of the person who has made him a son and so brings him up. In his case, neither the vital seed of which he is born nor the soil in which he is born, becomes the cause of sonship.” (Adiratha is the father of Karna and so is Pandu the father of Pandavas by this definition.)
Yudhishthira said, “What kind of a son is that who is said to be a made son and whose sonship arises from the fact of his being taken and brought up and in whose case neither the vital seed nor the soil of birth, O Bharata, is regarded as the cause of sonship?”
Bhishma said, “When a person takes up and rears a son that has been cast off on the road (or in the river in certain case) by his father or mother, and when the person thus taking and rearing him fails to find out his parents after search, he becomes the father of such a son and the latter becomes what is called his made son. Not having anybody to own him, he becomes owned by him who brings him up. Such a son, again, comes to be regarded as belonging to that order to which his owner or rearer belongs.”
This is exactly what Karna also told Krishna while declining. Karna knew of his real birth from early on and he knew the law as well as Krishna.
Pandu’s Kanina but abandoned son, Karna knew that he is “Made” son of Adiratha and would give him Pind rather to Pandu. In no circumstance Karna would be considered heir to the throne or heir to Vichitravirya. So even if Karna joins his uterine brothers, he will be a son of Adiratha in Pandava camp like he is son of Adiratha in Kaurava camp now.
Krishna was just trying to weaken his resolve to fight for Kauravas. Bheeshma also knew Karna was kanina son of Kunti and that Karna also knew this fact. He approached Karna in different way to force Karna to quit the War.
As results bear out, Bheeshma was more successful than Krishna. By the way, Adiratha was also a Kaurava and Bharata so Karna would be a Kuru or Bharata regardless of whether Kunti claims him or not.
(Then in Anushasana parva, Yudhisthara asks how to conduct Karna’s last rites and ranks they can accord his widows and children.)
Yudhishthira said, “How should the purificatory rites of such a person be performed? In whose case what sort of rites are to be performed? With what girl should he be wedded? Do thou tell me all this, O grandsire!”
Bhishma said, “The rites of purification touching such a son should be performed conformably to the usage of the person himself that raises him, for, cast off by his parents, such a son obtains the order of the person that takes him and brings him up. Indeed, O thou of unfading glory, the rearer should perform all the purificatory rites with respect to such a son according to the practices of the rearer’s own race and kinsmen. As regards the girl also, that should be bestowed in marriage upon such a son, who belongs to the order of the rearer himself.”
So as per Bheeshma, Karna is son of Adiratha (and Karna agreed to this in Udyoga Parva chapter 141, these two seldom agreed on anything!).
Pranshu B. Saxena