Tulsidas Ji was not unaware of the challenges which Sanatan Dharma was facing in his times and issues which had caused inherent weaknesses in the society. Two of the major debates or challenges which Tulsidas Ji attempted successfully to overcome are the Shaivite-Vaishnavite differences and the old Sagun-Nirgun Brahman debate, which was accentuated with the introduction of the later Abrahamic religions and their concept of God, in India through years of invasions and intermingling.

1. Shaivites and Vaishnavites

Bhagwan Shiva (the destroyer), Bhagwan Vishnu (the Preserver) and Brahma (the Creator) make up the trinity of supreme Gods in Sanatan Dharma as it exists today. There have been instances of disharmony between followers of Shiva and followers of Vishnu, with each claiming superiority ovethech other. Tulsidas Ji has harmonised the situation by claiming that Sri Ram (Vishnu) does not bestow his devotion on people who do not love Bhagwan Shiva.

सिव पद कमल जिन्हहि रति नाहीं । रामहि ते सपनेहुँ न सोहाहीं ⁠।⁠।
बिनु छल बिस्वनाथ पद नेहू । राम भगत कर लच्छन एहू ⁠।⁠।
Shri Ram does not have any liking even in dreams, for people who do not have love for the lotus feet of Shiva. Pure love for Shiva without any guile is a trait of devotees of Ram.

दो०—औरउ एक गुपुत मत सबहि कहउँ कर जोरि ⁠।

संकर भजन बिना नर भगति न पावइ मोरि ⁠।⁠।⁠

There is another secret belief, which I am telling with folded hands. Without worshipping Shankarji, no man can attain devotion in me.

सिव द्रोही मम भगत कहावा ।

सो नर सपनेहुँ मोहि न पावा ⁠।⁠।

संकर बिमुख भगति चह मोरी ।

सो नारकी मूढ़ मति थोरी ⁠।⁠।

The person who is hostile to Shiva does not find me even in a dream although he may be known as my devotee. One who seeks my devotion and simultaneously opposes Shankarji is foolish, worthy of hell, and has low intelligence.

2. Sagun-Nirgun Debate

Tulsidas Ji has repeated several times in Ramcharitmanas that there is no difference between the two and that Nirgun Brahman takes Sagun form due to the love of devotees. While explaining the same, Tulsidas Ji has explained complex concepts of Brahman, Jivatma or Jiva and Maya in very simple language using a minimum amount of words without losing the beauty of the poetry.

अगुन सगुन दुइ ब्रह्म सरूपा ।

अकथ अगाध अनादि अनूपा ⁠।⁠।

मोरें मत बड़ नामु दुहू तें ।

किए जेहिं जुग निज बस निज बूतें ⁠।⁠।

Nirgun & Sagun (Attributeless and with attributes) are both forms of Brahman (Parmatma). It (Brahman) is beyond words, infinite, without an end and unique. In my (TulsiDas Ji) opinion, the name recitation (japa) is even bigger than these two forms (of Brahman), as it has control over both of them, through its power.

सगुनहि अगुनहि नहिं कछु भेदा ।

गावहिं मुनि पुरान बुध बेदा ⁠।⁠।

अगुन अरूप अलख अज जोई ।

भगत प्रेम बस सगुन सो होई ⁠।⁠।

Munis, Puranas, Wise and Vedas sing that there is no difference between Sagun and Nirgun. That which is attributeless, without form, beyond description and without any origin takes Saguna form to reciprocate  love of devotees.

आगें रामु लखनु बने पाछें ।

तापस बेष बिराजत काछें ⁠।⁠।

उभय बीच सिय सोहति कैसें ।

ब्रह्म जीव बिच माया जैसें ⁠।⁠।

Both Ram (walking) in front and Laxman following him are looking resplendent dressed as Tapasvi. How is graceful Sita looking between the two? As Maya is there between Brahman and Jeeva.

जो गुन रहित सगुन सोइ कैसें ।

जलु हिम उपल बिलग नहिं जैसें ⁠।⁠।

जासु नाम भ्रम तिमिर पतंगा ।

तेहि किमि कहिअ बिमोह प्रसंगा ⁠।⁠।

How come the one who is attributeless is the same as Saguna? Just like there is no difference between water and hail. How can one be thought of as illusion, whose name itself is like fire which liberates ephemeral flies of illusion?.