​MN 115 Bahudhatuka Sutta: The Many Kinds of Elements 

​Thus have i heard.

On one occasion the Blessed One was living at Savatthi in Jeta's Grove, Anathapindika's Park. There he addressed the bhikkhus thus: "Bhikkhus, whatever fears arise, all arise because of the fool, not because of the wise man; whatever troubles arise, all arise because of the fool, not because of the wise man; whatever calamities arise, all arise because of the fool, not because of the wise man. Just as a fire that starts in a shed made of rushes or grass burns down even a house with a peaked roof, with walls plastered inside and outside, shut off, secured by bars, with shuttered windows; so too, bhikkhus, whatever fears arise.;.all arise because of the fool, not because of the wise man. "

"Thus: the fool brings fear, the wise man brings no fear; the fool brings trouble, the wise man brings no trouble; the fool brings calamity, the wise man brings no calamity. No fear comes from the wise man, no trouble comes from the wise man, no calamity comes from the wise man. Therefore, bhikkhus, you should train thus: 'We shall be wise men, we shall be inquirers.'"

When this was said, the venerable Ananda asked the Blessed One: "In what way, venerable sir, can a bhikkhu be called a wise man and an inquirer?"
Buddha: "When, Ananda, a bhikkhu is skilled in the elements, skilled in the bases, skilled in dependent origination, skilled in what is possible and what is impossible, in that way he can be called a wise man and an inquirer." 
THE ELEMENTS

Ananda: "But, venerable sir, in what way can a bhikkhu be called skilled in the elements?"
Buddha: "There are, Ananda, these eighteen elements: the eye element, the form element, the eye-consciousness element; the ear element, the sound element, the ear-consciousness element; the nose element, the odor element, the nose-consciousness element; the tongue element, the flavor element, the tongue consciousness element; the body element, the tangible element, the body-consciousness element; the mind element, the mind-object element, the mind-consciousness element. When he knows and sees these eighteen elements, a bhikkhu can be called skilled in the elements."

Ananda: "But, venerable sir, might there be another way in which a bhikkhu can be called skilled in the elements?" Buddha: "There might be, Ananda. There are, Ananda, these six elements: the earth element, the water element, the fire element, the air element, the space element, and the consciousness element. When he knows and sees these six elements, a bhikkhu can be called skilled in the elements."

Ananda: "But, venerable sir, might there be another way in which a bhikkhu can be called skilled in the elements?" Buddha: "There might be, Ananda. There are, Ananda, these six elements: the pleasure element, the pain element, the joy element, the grief element, the equanimity element, and the ignorance element. When he knows and sees these six elements, a bhikkhu can be called skilled in the elements."

Ananda: "But, venerable sir, might there be another way in which a bhikkhu can be called skilled in the elements?" Buddha: "There might be, Ananda. There are, Ananda, these six elements: the sensual desire element, the renunciation element, the ill will element, the non-ill will element, the cruelty element, and the non-cruelty element. When he knows and sees these six elements, a bhikkhu can be called skilled in the elements."

Ananda: "But, venerable sir, might there be another way in which a bhikkhu can be called skilled in the elements?" Buddha: "There might be, Ananda. There are, Ananda, these three elements: the sense-sphere element, the fine-material element, and the immaterial element. When he knows and sees these three elements, a bhikkhu can be called skilled in the elements."

Ananda: "But, venerable sir, might there be another way in which a bhikkhu can be called skilled in the elements?" Buddha: "There might be, Ananda. There are, Ananda, these two elements: the conditioned element and the unconditioned element. When he knows and sees these two elements, a bhikkhu can be called skilled in the elements.
THE BASES

Ananda: "But, venerable sir, in what way can a bhikkhu be called skilled in the bases?"
Buddha: "There are, Ananda, these six internal and external bases: the eye and forms, the ear and sounds, the nose and odors, the tongue and flavors, the body and tangibles, the mind and mind-objects.When he knows and sees these six internal and external bases, a bhikkhu can be called skilled in the bases." 

DEPENDENT ORIGINATION

Ananda:"But, venerable sir, in what way can a bhikkhu be called skilled in dependent origination?"
Buddha: "Here, Ananda, a bhikkhu knows thus: 'When this exists, that comes to be; with the arising of this, that arises. When this does not exist, that does not come to be; with the cessation of this, that ceases. That is, with ignorance as condition, formations come to be; with formations as condition, consciousness; with consciousness as condition, mentality-materiality; with mentalitymateriality as condition, the sixfold base; with the sixfold base as condition, contact; with contact as condition, feeling; with feeling as condition, craving; with craving as condition, clinging; with clinging as condition, being; with being as condition, birth; with birth as condition, ageing and death, sorrow, lamentation, pain, grief, and despair come to be. Such is the origin of this whole mass of suffering. '"

"But with the remainder-less fading away and cessation of ignorance comes cessation of formations; with the cessation of formations, cessation of consciousness; with the cessation of consciousness, cessation of mentality-materiality; with the cessation of mentality-materiality, cessation of the sixfold base; with the cessation of the sixfold base, cessation of contact; with the cessation of contact, cessation of feeling; with the cessation of feeling, cessation of craving; with the cessation of craving, cessation of clinging; with the cessation of clinging, cessation of being; with the cessation of being, cessation of birth; with the cessation of birth, ageing and death, sorrow, lamentation, pain, grief, and despair cease. Such is the cessation of this whole mass of suffering.' In this way, Ananda, a bhikkhu can be called skilled in dependent origination." 
THE POSSIBLE AND THE IMPOSSIBLE

Ananda: "But, venerable sir, in what way can a bhikkhu be called skilled in what is possible and what is impossible?" Buddha: "Here, Ananda, a bhikkhu understands: 'It is impossible, it cannot happen that a person possessing right view could treat any formation as permanent - there is no such possibility.' And he understands: 'It is possible that an ordinary person might treat some formation as permanent - there is such a possibility.' He understands: 'It is impossible, it cannot happen that a person possessing right view could treat any formation as pleasurable - there is no such possibility.' And he understands: 'It is possible that an ordinary person might treat some formation as pleasurable - there is such a possibility.' "

"He understands: 'It is impossible, it cannot happen that a person possessing right view could treat anything as self - there is no such possibility.' And he understands: 'It is possible that an ordinary person might treat something as self - there is such a possibility.' He understands: 'It is impossible, it cannot happen that a person possessing right view could deprive his mother of life there is no such possibility.' And he understands: 'It is possible that an ordinary person might deprive his mother of life - there is such a possibility.' He understands: 'It is impossible, it cannot happen that a person possessing right view could deprive his father of life...could deprive an arahant of life - there is no such possibility.' And he understands: 'It is possible that an ordinary person might deprive his father of life...might deprive an arahant of life - there is such a possibility.'"

"He understands: 'It is impossible, it cannot happen that a person possessing right view could, with a mind of hate, shed a Tathagata's blood there is no such possibility.' And he understands: 'It is possible that an ordinary person might, with a mind of hate, shed a Tathagata's blood - there is such a possibility.' He understands: 'It is impossible, it cannot happen that a person possessing right view could cause a schism in the Sangha...could acknowledge another teacher- there is no such possibility.' And he understands: 'It is possible that an ordinary person might cause a schism in the Sangha...might acknowledge another teacher there is such a possibility.' "

" 'He understands: 'It is impossible, it cannot happen that two Accomplished Ones, Fully Enlightened Ones, could arise contemporaneously in one world-system - there is no such possibility.'And he understands: 'It is possible that one Accomplished One, a Fully Enlightened One, might arise in one world-system - there is such a possibility.' He understands: 'It is impossible, it cannot happen that two Wheel-turning Monarchs could arise contemporaneously in one world-system...It is possible that one Wheel-turning Monarch might arise in one world system - there is such a possibility.'  He understands: 'It is impossible, it cannot happen that a woman could be an Accomplished One, a Fully Enlightened One - there is no such possibility.'"

" And he understands: 'It is possible that a man might be an Accomplished One, a Fully Enlightened One - there is such a possibility.' He understands: 'It is impossible, it cannot happen that a woman could be a Wheel-turning Monarch.. .that a woman could occupy the position of Sakka ...that a woman could occupy the position of Mara...that a woman could occupy the position of Brahma — there is no such possibility.' And he understands: 'It is possible that a man might be a Wheel-turning Monarch...that a man might occupy the position of Sakka...that a man might occupy the position of Mara...that a man might occupy the position of Brahma - there is such a possibility.' He understands: 'It is impossible, it cannot happen that an unwished for, undesired, disagreeable result could be produced from good bodily conduct...from good verbal conduct...from good mental conduct - there is no such possibility.' And he understands: 'It is possible that a wished for, desired, agreeable result ​might be produced from good bodily conduct.. .from good verbal conduct.. .from good mental conduct - there is such a possibility.' "
"He understands: 'It is impossible, it cannot happen that a person engaging in bodily misconduct .. .engaging in verbal misconduct...engaging in mental misconduct could on that account, for that reason, on the dissolution of the body, after death, reappear in a happy destination, even in the heavenly world - there is no such possibility.' And he understands: 'It is possible that a person engaging in bodily misconduct...engaging in verbal misconduct.. .engaging in mental misconduct might on that account, for that reason, on the dissolution of the body, after death, reappear in a state of deprivation, in an unhappy destination, in perdition, even in hell - there is such a possibility.'"

"He understands: 'It is impossible, it cannot happen that a person engaging in good bodily conduct.. .engaging in good verbal conduct...engaging in good mental conduct could on that account, for that reason, on the dissolution of the body, after death, reappear in a state of deprivation, in an unhappy destination, in perdition, even in hell - there is no such possibility.' And he understands: 'It is possible that a person engaging in good bodily conduct...engaging in good verbal conduct... engaging in good mental conduct might on that account, for that reason, on the dissolution of the body, after death, reappear in a happy destination, even in the heavenly world.' "

In this way, Ananda, a bhikkhu can be called skilled in what is possible and what is impossible." 

CONCLUSION

When this was said, the venerable Ananda said to the Blessed One: "It is wonderful, venerable sir, it is marvellous! What is the name of this discourse on the Dhamma?"
Buddha: "You may remember this discourse on the Dhamma, Ananda, as 'The Many Kinds of Elements' and as 'The Four Cycles' and as 'The Mirror of the Dhamma' and as 'The Drum of the Deathless' and as 'The Supreme Victory in Battle.'" 

That is what the Blessed One said. The venerable Ananda was satisfied and delighted in the Blessed One's words. 
​In summary, this discourse contains a series of questions asked by Venerable Ananda and Buddha answered them one by one. Beginning by praising a wise person, the Buddha goes on to explain that one becomes wise by inquiring into the elements, sense bases, dependent origination, and what is possible and impossible.
References: 
1. www.accesstoinsight.org
2. https://suttacentral.net/
3. The middle length discourses of the Buddha (Bhikkhu Bodhi)