In actuality, all souls are devotees, jīvera svarūpa haya kṛṣṇera nitya dāsa [Cc. Madhya-līlā 20.108]. The constitutional position of the jīvas, the living entities, their real identity is that they are bhaktas, devotees of the Lord. The soul is an eternal devotee, an eternal servant of Lord Kṛṣṇa, but has forgotten this. 
Jīva is the marginal potency. The touch of two: spiritual and material, and the jīva has minute independence. Jīva is the taṭastha śakti, or marginal potency, which means two are present: superior and inferior. Therefore, it's marginal. The Sanskṛt word taṭa means margin, where two things touch. This land touches water, so this is known as the margin.

Similarly, marginal potency means two potencies are there: superior and inferior. The two are there. The jīva is touched with these two and has minute independence to choose. The jīva has a choice whether to choose superior or inferior śakti, potency. Therefore, taṭastha śakti, marginal potency means that two: parā and aparā, superior and inferior, or internal and external energies are present. The living entity is in between and in touch with these two energies: parā and aparā, superior and inferior. There is one example cited of a frog. A frog may live on the land and in the water. It may be aquatic or may not be aquatic. We say ubhayachara prāṇi, which means both. A frog can live both on land and in water. Sometimes he chooses to live in the water and sometimes on land. 

Similarly, the living entity can live under parā prakṛti, superior nature, or can live under inferior nature, aparā prakṛti, also known as material nature, as he desires. It depends upon the desire or willingness of the living entities. Both parā and aparā prakṛtis have touched the living entity, and the living entity has minute independence, so he may exercise his independence to live under parā, superior energy, or under aparā, inferior energy. But naturally or constitutionally, living entities belong to superior energy. So, when that living entity lives under superior energy or parā prakṛti, he is situated in his original constitutional position.

Consequently, when he lives under aparā prakṛti, the inferior energy, he is not in his constitutional position. In other words, when the living entity utilizes its minute independence properly, it lives under parā prakṛti. On the other hand, when he misuses or abuses his minute independence, he lives under aparā prakṛti. In this way, he becomes captured by māyā, he forgets his constitutional position or identity, and he forgets the Lord, Supreme Lord. Thus, he is caught up by material energy or material nature and is encaged in the material world, suffering birth, death, old age, and disease life after life unless he becomes situated in his constitutional position.