In addition to the single conclusive presumption, there are several rebuttable presumptions which may result in a man being presumed to be the natural father of a child. The core theme of the first three of these rebuttable presumptions is the marriage (or attempted marriage) of the natural father to the natural mother. Thus the statute begins with a rebuttable presumption for situations in which a child is either born during a marriage (even if not conceived during it) or might have been conceived during it, and follows it up with similar presumptions in cases of invalid marriages and cases where the father marries or attempts to marry the natural mother after the child is born, See Family Code section 7611, subdivisions (b) and (c). Another rebuttable presumption occurs when a man receives a child into his home and openly holds out the child as his natural child. ( 7611, subd. (d).) The text of the Family Code section 7611, subdivision (a) is: "A man is presumed to be the natural father of a child if he meets the conditions provided in Chapter 1 (commencing with section 7540 i.e., the conclusive presumption) or Chapter 3 (commencing with Section 7570 which provides for a system of voluntary paternity in the case of unwed mothers) of Part 2 or in any of the following subdivisions: (a) He and the child's natural mother are or have been married to each other and the child is born during the marriage, or within 300 days after the marriage is terminated by death, annulment, declaration of invalidity, or divorce, or after a judgment of separation is entered by a court." Because there are several rebuttable presumptions of natural fatherhood, a separate statute, Family Code section 7612, subdivision (b), deals with the problem of what happens when two or more of the presumptions collide. Section 7612, subdivision (b) requires courts to favor the presumption which "is founded on the weightier considerations of policy and logic." (See Fam. Code, 7612, subd. (b) "If two or more presumptions arise under Section 7611 which conflict with each other, the presumption which on the facts is founded on the weightier considerations of policy and logic controls".)