Juridical capacity (Article 37, Civil Code)

Juridical capacity, which is the fitness to be the subject of legal relations, is inherent in every natural person and is lost only through death. Capacity to act, which is the power to do acts with legal effect, is acquired and may be lost. (Article 37, Civil Code)

Juridical capacity is the fitness to be the subject of legal relations; it is inherent in every natural person. Capacity to act is the power to do acts with legal effect; it may be acquired and it may also be lost; it is acquired upon the attainment of the age of majority.
A person is a physical or legal being susceptible of rights and obligations or of being the subject of legal relations.

A right is the power which a person has to demand from another a prestation or the power to do or not to do, or to demand something. On the other hand, an obligation is the juridical necessity to give, to do or not to do. From the viewpoint of another wielding a right, the debtor or obligor's obligation is the very reason the right exists in the first place; from the viewpoint of another shouldering an obligation, the creditor or obligee's right is the very reason why the obligation has to be performed, paid, fulfilled or accomplished.

Juridical capacity is an inherent and ineffaceable attribute of man; it attaches to him by the mere fact of his being a man and is lost only through death. Capacity to act, on the other hand, is acquired and may be lost. The former can exist without the latter, but the existence of the latter always implies that of the former. The union of these two is the full civil capacity. (Sanchez Roman, 112-113; 1 Vaverde, 212)

In one case, Continental Steel v. Montaño (G.R. No. 182836, October 13, 2009, the Supreme Court was faced with a unique question. It was whether or not the father-employee is entitled to death benefits under a collective bargaining agreement (CBA) when his wife suffered a miscarriage. According to the employer, no, he is not entitled to such benefit because the child was never born and, as a result, it had no juridical capacity and no capacity to act. The Supreme Court sided with the parent and said: "We need not establish civil personality of the unborn child herein since his/her juridical capacity and capacity to act as a person are not in issue. It is not a question before us whether the unborn child acquired any rights or incurred any obligations prior to his/her death that were passed on to or assumed by the child’s parents. The rights to bereavement leave and other death benefits in the instant case pertain directly to the parents of the unborn child upon the latter’s death."

The Supreme Court continued to explain:
Death has been defined as the cessation of life. Life is not synonymous with civil personality. One need not acquire civil personality first before he/she could die. Even a child inside the womb already has life. No less than the Constitution recognizes the life of the unborn from conception, that the State must protect equally with the life of the mother. If the unborn already has life, then the cessation thereof even prior to the child being delivered, qualifies as death.

Likewise, the unborn child can be considered a dependent under the CBA. As Continental Steel itself defines, a dependent is "one who relies on another for support; one not able to exist or sustain oneself without the power or aid of someone else." Under said general definition, even an unborn child is a dependent of its parents. Hortillano’s child could not have reached 38-39 weeks of its gestational life without depending upon its mother, Hortillano’s wife, for sustenance. Additionally, it is explicit in the CBA provisions in question that the dependent may be the parent, spouse, or child of a married employee; or the parent, brother, or sister of a single employee. The CBA did not provide a qualification for the child dependent, such that the child must have been born or must have acquired civil personality, as Continental Steel avers. Without such qualification, then child shall be understood in its more general sense, which includes the unborn fetus in the mother’s womb.

The capacity (to act) of natural and juridical persons (legal persons), in general, determines whether they may make binding amendments to their rights, duties, and obligations, such as getting married or merging, entering into contracts, making gifts, or writing a valid will.  [en.wikipedia.org/wiki/Capacity_(law)] 

In law, a legal person is any person or 'thing' (less ambiguously, any legal entity) that can do the things an everyday person can usually do in law – such as enter into contracts, sue and be sued, own property, and so on. The reason for the term "legal person" is that some legal persons are not people: companies and corporations are "persons" legally speaking (they can legally do most of the things an ordinary person can do), but they are clearly not people in the ordinary sense. There are therefore two kinds of legal entities: human and non-human. In law, a human person is called a natural person (sometimes also a physical person), and a non-human person is called a juridical person (sometimes also a juridic, juristic, artificial, legal, or fictitious person, Latin: persona ficta). [https://en.wikipedia.org/wiki/Legal_person]