SB 3.29.1-2

devahūtir uvāca
lakṣaṇaṁ mahad-ādīnāṁ
 prakṛteḥ puruṣasya ca
svarūpaṁ lakṣyate ’mīṣāṁ
 yena tat-pāramārthikam
yathā sāṅkhyeṣu kathitaṁ
 yan-mūlaṁ tat pracakṣate
bhakti-yogasya me mārgaṁ
 brūhi vistaraśaḥ prabho
Synonyms: 
devahūtiḥ uvāca — Devahūti said; lakṣaṇam — symptoms; mahat-ādīnām — of the mahat-tattva and so on; prakṛteḥ — of material nature; puruṣasya — of the spirit; ca — and; svarūpam — the nature; lakṣyate — is described; amīṣām — of those; yena — by which; tat-pārama-arthikam — the true nature of them; yathā — as; sāṅkhyeṣu — in Sāṅkhya philosophy; kathitam — is explained; yat — of which; mūlam — ultimate end; tat — that; pracakṣate — they call; bhakti-yogasya — of devotional service; me — to me; mārgam — the path; brūhi — please explain; vistaraśaḥ — at length; prabho — my dear Lord Kapila.
Translation: 
Devahūti inquired: My dear Lord, You have already very scientifically described the symptoms of the total material nature and the characteristics of the spirit according to the Sāṅkhya system of philosophy. Now I shall request You to explain the path of devotional service, which is the ultimate end of all philosophical systems.
Purport: 

In this Twenty-ninth Chapter, the glories of devotional service are elaborately explained, and the influence of time on the conditioned soul is also described. The purpose of elaborately describing the influence of time is to detach the conditioned soul from his material activities, which are considered to be simply a waste of time. In the previous chapter, material nature, the spirit and the Supreme Lord, or Supersoul, are analytically studied, and in this chapter the principles of bhakti-yoga, or devotional service — the execution of activities in the eternal relationship between the living entities and the Personality of Godhead — are explained.

Bhakti-yoga, devotional service, is the basic principle of all systems of philosophy; all philosophy which does not aim for devotional service to the Lord is considered merely mental speculation. But of course bhakti-yoga with no philosophical basis is more or less sentiment. There are two classes of men. Some consider themselves intellectually advanced and simply speculate and meditate, and others are sentimental and have no philosophical basis for their propositions. Neither of these can achieve the highest goal of life — or, if they do, it will take them many, many years. Vedic literature therefore suggests that there are three elements — namely the Supreme Lord, the living entity and their eternal relationship — and that the goal of life is to follow the principles of bhakti, or devotional service, and ultimately attain to the planet of the Supreme Lord in full devotion and love as an eternal servitor of the Lord.

Sāṅkhya philosophy is the analytical study of all existence. One has to understand everything by examining its nature and characteristics. This is called acquirement of knowledge. But one should not simply acquire knowledge without reaching the goal of life or the basic principle for acquiring knowledge — bhakti-yoga. If we give up bhakti-yoga and simply busy ourselves in the analytical study of the nature of things as they are, then the result will be practically nil. It is stated in the Bhāgavatam that such engagement is something like husking a paddy. There is no use beating the husk if the grain has already been removed. By the scientific study of material nature, the living entity and the Supersoul, one has to understand the basic principle of devotional service to the Lord.