Why do viṣaya-vāsanās sprout as thoughts, and how to eradicate them?

A friend wrote to me recently:

Through self-inquiry every vasana comes up to the surface. Sometimes I am really lost, sometimes I am cool.

I try to practise self-inquiry with every thought that comes up in my mind, but they are getting more and more.

Is it true that vasanas want to go, when they are on the surface?

The best thing is, I will not give up to practise, but I want to do it in the best way.

The following is adapted from the reply I wrote to him:

In what sense does Bhagavan generally use the terms பொருள் (poruḷ) and வஸ்து (vastu)?

In my previous article, Uḷḷadu Nāṟpadu first maṅgalam verse: what exists is only thought-free awareness, which is called ‘heart’, so being as it is is alone meditating on it, I translated the term ‘உள்ளபொருள்’ (uḷḷa-poruḷ), which Bhagavan uses in the first and third lines of the first maṅgalam verse of Uḷḷadu Nāṟpadu, as ‘the existing substance’, ‘actual substance’ or ‘real substance’, and I explained that உள்ள (uḷḷa) is a relative or adjectival participle that means ‘existing’, ‘actual’ or ‘real’, and பொருள் (poruḷ) is a noun that has a range of meanings, including thing (any thing, but particularly a thing that really exists or a thing of value), meaning, subject-matter, substance, essence, reality or wealth, but in this context means ‘substance’ or ‘reality’.

In a comment on that article a friend called Mouna asked me why I chose to translate பொருள் (poruḷ) as ‘substance’ rather than ‘reality’:

Uḷḷadu Nāṟpadu first maṅgalam verse: what exists is only thought-free awareness, which is called ‘heart’, so being as it is is alone meditating on it

As I explained in my previous article, Upadēśa Kaliveṇbā: the extended version of Uḷḷadu Nāṟpadu, over the coming months (or perhaps years, if other work gets in my way) I hope to be able to publish a series of forty-two articles each of which will be a detailed explanation of one of the verses of Uḷḷadu Nāṟpadu along with its kaliveṇbā extension or extensions, so this article is the first in this series.

No commentary on the verses of Uḷḷadu Nāṟpadu can be considered complete or entirely comprehensive, because however much one may explain and discuss them there will always be room for further explanations and discussions from different perspectives, so the explanations I will be giving in this series of articles will be far from complete. However my aim is to give at least a basic explanation of each verse, enough to make its profound and rich meaning clear and to enable each reader to do their own reflection (manana) on it.