ΤΙ. γῆν μὲν γὰρ ἀσύστατον ὑπὸ βίας οὕτως ὕδωρ μόνον λύει, συνεστηκυῖαν δὲ πλὴν πυρὸς οὐδέν· εἴσοδος γὰρ οὐδενὶ πλὴν πυρὶ λέλειπται. τὴν δὲ ὕδατος αὖ σύνοδον τὴν μὲν βιαιοτάτην πῦρ μόνον, τὴν δὲ ἀσθενεστέραν ἀμφότερα, πῦρ τε καὶ ἀήρ, διαχεῖτον, ὁ μὲν κατὰ τὰ διάκενα, τὸ δὲ καὶ κατὰ τὰ τρίγωνα· βίᾳ δὲ ἀέρα συστάντα οὐδὲν λύει πλὴν κατὰ τὸ στοιχεῖον, ἀβίαστον δὲ κατατήκει μόνον πῦρ. τὰ δὴ τῶν συμμείκτων ἐκ γῆς τε καὶ ὕδατος σωμάτων, μέχριπερ ἂν ὕδωρ αὐτοῦ τὰ τῆς γῆς διάκενα καὶ βίᾳ συμπεπιλημένα κατέχῃ, τὰ μὲν ὕδατος ἐπιόντα ἔξωθεν εἴσοδον οὐκ ἔχοντα μέρη περιρρέοντα τὸν ὅλον ὄγκον ἄτηκτον εἴασεν, τὰ δὲ πυρὸς εἰς τὰ τῶν ὑδάτων διάκενα εἰσιόντα, ὅπερ ὕδωρ γῆν, τοῦτο πῦρ [ἀέρα] ἀπεργαζόμενα, τηχθέντι τῷ κοινῷ σώματι ῥεῖν μόνα αἴτια συμβέβηκεν· τυγχάνει δὲ ταῦτα ὄντα, τὰ μὲν ἔλαττον ἔχοντα ὕδατος ἢ γῆς, τό τε περὶ τὴν ὕαλον γένος ἅπαν ὅσα τε λίθων χυτὰ εἴδη καλεῖται, τὰ δὲ πλέον ὕδατος αὖ, πάντα ὅσα κηροειδῆ καὶ θυμιατικὰ σώματα συμπήγνυται. καὶ τὰ μὲν δὴ σχήμασι κοινωνίαις τε καὶ μεταλλαγαῖς εἰς ἄλληλα πεποικιλμένα εἴδη σχεδὸν ἐπιδέδεικται· τὰ δὲ παθήματα αὐτῶν διʼ ἃς αἰτίας γέγονεν πειρατέον ἐμφανίζειν. πρῶτον μὲν οὖν ὑπάρχειν αἴσθησιν δεῖ τοῖς λεγομένοις ἀεί, σαρκὸς δὲ καὶ τῶν περὶ σάρκα γένεσιν, ψυχῆς τε ὅσον θνητόν, οὔπω διεληλύθαμεν· τυγχάνει δὲ οὔτε ταῦτα χωρὶς τῶν περὶ τὰ παθήματα ὅσα αἰσθητικὰ οὔτʼ ἐκεῖνα ἄνευ τούτων δυνατὰ ἱκανῶς λεχθῆναι, τὸ δὲ ἅμα σχεδὸν οὐ δυνατόν. ὑποθετέον δὴ πρότερον θάτερα, τὰ δʼ ὑποτεθέντα ἐπάνιμεν αὖθις. ἵνα οὖν ἑξῆς τὰ παθήματα λέγηται τοῖς γένεσιν, ἔστω πρότερα ἡμῖν τὰ περὶ σῶμα καὶ ψυχὴν ὄντα. πρῶτον μὲν οὖν ᾗ πῦρ θερμὸν λέγομεν, ἴδωμεν ὧδε σκοποῦντες, τὴν διάκρισιν καὶ τομὴν αὐτοῦ περὶ τὸ σῶμα ἡμῶν γιγνομένην ἐννοηθέντες. ὅτι μὲν γὰρ ὀξύ τι τὸ πάθος, πάντες σχεδὸν αἰσθανόμεθα·
Thus earth when it is not forcibly condensed is dissolved only by water; and when it is condensed it is dissolved by fire only, since no entrance is left for anything save fire. Water, again, when most forcibly massed together is dissolved by fire only, but when massed less forcibly both by fire and air, the latter acting by way of the interstices, and the former by way of the triangles; but air when forcibly condensed is dissolved by nothing save by way of its elemental triangles, and when unforced it is melted down by fire only. As regards the classes of bodies which are compounds of earth and water, so long as the water occupies the interspaces of earth which are forcibly contracted, the portions of water which approach from without find no entrance, but flow round the whole mass and leave it undissolved. But when portions of fire enter into the interspaces of the water they produce the same effects on water as water does on earth; consequently, they are the sole causes why the compound substance is dissolved and flows. And of these substances those which contain less water than earth form the whole kind known as “glass,” and all the species of stone called “fusible”; while those which contain more water include all the solidified substances of the type of wax and frankincense. And now we have explained with some fullness the Four Kinds, which are thus variegated in their shapes and combinations and permutations; but we have still to try to elucidate the Causes which account for their affective qualities. Now, first of all, the quality of sense-perceptibility must always belong to the objects under discussion; but we have not as yet described the generation of flesh and the appurtenances of flesh, nor of that portion of Soul which is mortal. But, in truth, these last cannot be adequately explained apart from the subject of the sensible affections, nor the latter without the former; while to explain both simultaneously is hardly possible. Therefore, we must assume one of the two, to begin with, and return later to discuss our assumptions. In order, then, that the affective properties may be treated next after the kinds, let us presuppose the facts about body and soul. Firstly, then, let us consider how it is that we call fire “hot” by noticing the way it acts upon our bodies by dividing and cutting. That its property is one of sharpness we all, I suppose, perceive;
ΤΙ. τὴν δὲ λεπτότητα τῶν πλευρῶν καὶ γωνιῶν ὀξύτητα τῶν τε μορίων σμικρότητα καὶ τῆς φορᾶς τὸ τάχος, οἷς πᾶσι σφοδρὸν ὂν καὶ τομὸν ὀξέως τὸ προστυχὸν ἀεὶ τέμνει, λογιστέον ἀναμιμνῃσκομένοις τὴν τοῦ σχήματος αὐτοῦ γένεσιν, ὅτι μάλιστα ἐκείνη καὶ οὐκ ἄλλη φύσις διακρίνουσα ἡμῶν κατὰ σμικρά τε τὰ σώματα κερματίζουσα τοῦτο ὃ νῦν θερμὸν λέγομεν εἰκότως τὸ πάθημα καὶ τοὔνομα παρέσχεν. τὸ δʼ ἐναντίον τούτων κατάδηλον μέν, ὅμως δὲ μηδὲν ἐπιδεὲς ἔστω λόγου. τὰ γὰρ δὴ τῶν περὶ τὸ σῶμα ὑγρῶν μεγαλομερέστερα εἰσιόντα, τὰ σμικρότερα ἐξωθοῦντα, εἰς τὰς ἐκείνων οὐ δυνάμενα ἕδρας ἐνδῦναι, συνωθοῦντα ἡμῶν τὸ νοτερόν, ἐξ ἀνωμάλου κεκινημένου τε ἀκίνητον διʼ ὁμαλότητα καὶ τὴν σύνωσιν ἀπεργαζόμενα πήγνυσιν· τὸ δὲ παρὰ φύσιν συναγόμενον μάχεται κατὰ φύσιν αὐτὸ ἑαυτὸ εἰς τοὐναντίον ἀπωθοῦν. τῇ δὴ μάχῃ καὶ τῷ σεισμῷ τούτῳ τρόμος καὶ ῥῖγος ἐτέθη, ψυχρόν τε τὸ πάθος ἅπαν τοῦτο καὶ τὸ δρῶν αὐτὸ ἔσχεν ὄνομα. σκληρὸν δέ, ὅσοις ἂν ἡμῶν ἡ σὰρξ ὑπείκῃ, μαλακὸν δέ, ὅσα ἂν τῇ σαρκί· πρὸς ἄλληλά τε οὕτως. ὑπείκει δὲ ὅσον ἐπὶ σμικροῦ βαίνει· τὸ δὲ ἐκ τετραγώνων ὂν βάσεων, ἅτε βεβηκὸς σφόδρα, ἀντιτυπώτατον εἶδος, ὅτι τε ἂν εἰς πυκνότητα συνιὸν πλείστην ἀντίτονον ᾖ μάλιστα. βαρὺ δὲ καὶ κοῦφον μετὰ τῆς τοῦ κάτω φύσεως ἄνω τε λεγομένης ἐξεταζόμενον ἂν δηλωθείη σαφέστατα. φύσει γὰρ δή τινας τόπους δύο εἶναι διειληφότας διχῇ τὸ πᾶν ἐναντίους, τὸν μὲν κάτω, πρὸς ὃν φέρεται πάνθʼ ὅσα τινὰ ὄγκον σώματος ἔχει, τὸν δὲ ἄνω, πρὸς ὃν ἀκουσίως ἔρχεται πᾶν, οὐκ ὀρθὸν οὐδαμῇ νομίζειν· τοῦ γὰρ παντὸς οὐρανοῦ σφαιροειδοῦς ὄντος, ὅσα μὲν ἀφεστῶτα ἴσον τοῦ μέσου γέγονεν ἔσχατα, ὁμοίως αὐτὰ χρὴ ἔσχατα πεφυκέναι, τὸ δὲ μέσον τὰ αὐτὰ μέτρα τῶν ἐσχάτων ἀφεστηκὸς ἐν τῷ καταντικρὺ νομίζειν δεῖ πάντων εἶναι. τοῦ δὴ κόσμου ταύτῃ πεφυκότος, τί τῶν εἰρημένων ἄνω τις ἢ κάτω τιθέμενος οὐκ ἐν δίκῃ δόξει τὸ μηδὲν προσῆκον ὄνομα λέγειν; ὁ μὲν γὰρ μέσος ἐν αὐτῷ τόπος οὔτε κάτω πεφυκὼς οὔτε ἄνω λέγεσθαι δίκαιος, ἀλλʼ αὐτὸ ἐν μέσῳ· ὁ δὲ πέριξ οὔτε δὴ μέσος οὔτʼ ἔχων διάφορον αὑτοῦ μέρος ἕτερον θατέρου μᾶλλον πρὸς τὸ μέσον ἤ τι τῶν καταντικρύ. τοῦ δὲ ὁμοίως πάντῃ πεφυκότος ποῖά τις ἐπιφέρων ὀνόματα αὐτῷ ἐναντία καὶ πῇ καλῶς ἂν ἡγοῖτο λέγειν;
but as regards the thinness of its sides and the acuteness of its angles and the smallness of its particles and the rapidity of its motion—owing to all which properties fire is intense and keen and sharply cuts whatever it encounters,—these properties we must explain by recalling the origin of its form, how that it above all others is the one substance which so divides our bodies and minces them up as to produce naturally both that affection which we call “heat” and its very name. The opposite affection is evident, but none the less it must not lack description. When liquids with larger particles, which surround the body, enter into it they drive out the smaller particles; but as they cannot pass into their room they compress the moisture within us, so that in place of non-uniformity and motion they produce immobility and density, as a result of the uniformity and compression. But that which is being contracted contrary to nature fights, and, in accordance with its nature, thrusts itself away in the contrary direction. And to this fighting and shaking we give the names of “trembling” and “shivering”; while this affection as a whole, as well as the cause thereof, is termed “cold.” By the term “hard” we indicate all the things to which our flesh gives way; and by the term “soft” all those which give way to our flesh; and these terms are similarly used relatively to each other. Now a substance gives way when it has its base small; but when it is constructed of quadrangular bases, being very firmly based, it is a most inelastic form; and so too is everything which is of very dense composition and most rigid. The nature of “heavy” and “light” would be shown most clearly if, along with them, we examined also the nature of “above” and “below,” as they are called. That there really exist two distinct and totally opposite regions, each of which occupies one-half of the Universe—the one termed “below,” towards which move all things possessing any bodily mass, and the other “above,” towards which everything goes against its will,— this is a wholly erroneous supposition For inasmuch as the whole Heaven is spherical, all its outermost parts, being equally distant from the center, must really be “outermost” in a similar degree; and one must conceive of the center, which is distant from all the outermost parts by the same measures, as being opposite to them all. Seeing, then, that the Cosmos is actually of this nature, which of the bodies mentioned can one set “above” or “below” without incurring justly the charge of applying a wholly unsuitable name? For its central region cannot rightly be termed either “above” or “below,” but just “central”; while its circumference neither is central nor has it any one part more divergent than another from the center or any of its opposite parts. But to that which is in all ways uniform, what opposite names can we suppose are rightly applicable, or in what sense?
ΤΙ. εἰ γάρ τι καὶ στερεὸν εἴη κατὰ μέσον τοῦ παντὸς ἰσοπαλές, εἰς οὐδὲν ἄν ποτε τῶν ἐσχάτων ἐνεχθείη διὰ τὴν πάντῃ ὁμοιότητα αὐτῶν· ἀλλʼ εἰ καὶ περὶ αὐτὸ πορεύοιτό τις ἐν κύκλῳ, πολλάκις ἂν στὰς ἀντίπους ταὐτὸν αὐτοῦ κάτω καὶ ἄνω προσείποι. τὸ μὲν γὰρ ὅλον, καθάπερ εἴρηται νυνδή, σφαιροειδὲς ὄν, τόπον τινὰ κάτω, τὸν δὲ ἄνω λέγειν ἔχειν οὐκ ἔμφρονος· ὅθεν δὲ ὠνομάσθη ταῦτα καὶ ἐν οἷς ὄντα εἰθίσμεθα διʼ ἐκεῖνα καὶ τὸν οὐρανὸν ὅλον οὕτω διαιρούμενοι λέγειν, ταῦτα διομολογητέον ὑποθεμένοις τάδε ἡμῖν. εἴ τις ἐν τῷ τοῦ παντὸς τόπῳ καθʼ ὃν ἡ τοῦ πυρὸς εἴληχε μάλιστα φύσις, οὗ καὶ πλεῖστον ἂν ἠθροισμένον εἴη πρὸς ὃ φέρεται, ἐπεμβὰς ἐπʼ ἐκεῖνο καὶ δύναμιν εἰς τοῦτο ἔχων, μέρη τοῦ πυρὸς ἀφαιρῶν ἱσταίη τιθεὶς εἰς πλάστιγγας, αἴρων τὸν ζυγὸν καὶ τὸ πῦρ ἕλκων εἰς ἀνόμοιον ἀέρα βιαζόμενος δῆλον ὡς τοὔλαττόν που τοῦ μείζονος ῥᾷον βιᾶται· ῥώμῃ γὰρ μιᾷ δυοῖν ἅμα μετεωριζομένοιν τὸ μὲν ἔλαττον μᾶλλον, τὸ δὲ πλέον ἧττον ἀνάγκη που κατατεινόμενον συνέπεσθαι τῇ βίᾳ, καὶ τὸ μὲν πολὺ βαρὺ καὶ κάτω φερόμενον κληθῆναι, τὸ δὲ σμικρὸν ἐλαφρὸν καὶ ἄνω. ταὐτὸν δὴ τοῦτο δεῖ φωρᾶσαι δρῶντας ἡμᾶς περὶ τόνδε τὸν τόπον. ἐπὶ γὰρ γῆς βεβῶτες γεώδη γένη διιστάμενοι, καὶ γῆν ἐνίοτε αὐτήν, ἕλκομεν εἰς ἀνόμοιον ἀέρα βίᾳ καὶ παρὰ φύσιν, ἀμφότερα τοῦ συγγενοῦς ἀντεχόμενα, τὸ δὲ σμικρότερον ῥᾷον τοῦ μείζονος βιαζομένοις εἰς τὸ ἀνόμοιον πρότερον συνέπεται· κοῦφον οὖν αὐτὸ προσειρήκαμεν, καὶ τὸν τόπον εἰς ὃν βιαζόμεθα, ἄνω, τὸ δʼ ἐναντίον τούτοις πάθος βαρὺ καὶ κάτω. ταῦτʼ οὖν δὴ διαφόρως ἔχειν αὐτὰ πρὸς αὑτὰ ἀνάγκη διὰ τὸ τὰ πλήθη τῶν γενῶν τόπον ἐναντίον ἄλλα ἄλλοις κατέχειν—τὸ γὰρ ἐν ἑτέρῳ κοῦφον ὂν τόπῳ τῷ κατὰ τὸν ἐναντίον τόπον ἐλαφρῷ καὶ τῷ βαρεῖ τὸ βαρὺ τῷ τε κάτω τὸ κάτω καὶ τὸ ἄνω τῷ ἄνω πάντʼ ἐναντία καὶ πλάγια καὶ πάντως διάφορα πρὸς ἄλληλα ἀνευρεθήσεται γιγνόμενα καὶ ὄντα—τόδε γε μὴν ἕν τι διανοητέον περὶ πάντων αὐτῶν, ὡς ἡ μὲν πρὸς τὸ συγγενὲς ὁδὸς ἑκάστοις οὖσα βαρὺ μὲν τὸ φερόμενον ποιεῖ, τὸν δὲ τόπον εἰς ὃν τὸ τοιοῦτον φέρεται, κάτω, τὰ δὲ τούτοις ἔχοντα ὡς ἑτέρως θάτερα. περὶ δὴ τούτων αὖ τῶν παθημάτων ταῦτα αἴτια εἰρήσθω.
For suppose there were a solid body evenly-balanced at the center of the universe, it would never be carried away to the extremities because of their uniformity in all respects; nay, even were a man to travel round it in a circle he would often call the same part of it both “above” and “below,” according as he stood now at one pole, now at the opposite. For seeing that the Whole is, as we said just now, spherical, the assertion that it has one region “above” and one “below” does not become a man of sense. Now the origin of these names and their true meaning which accounts for our habit of making these verbal distinctions even about the whole Heaven, we must determine on the basis of the following principles. Suppose that a man were to take his stand in that region of the Universe in which the substance of fire has its special abode, and where also that substance to which it flies is collected in largest bulk; and suppose that, having the power to do so, he were to separate portions of the fire and weigh them, putting them on scales and lifting the balance and pulling the fire by force into the dissimilar air, it is obvious that he will force the smaller mass more easily than the larger. For if two masses are lifted up simultaneously by a single effort, the smaller will necessarily yield more and the larger less, owing to its resistance, to the force exerted; and the large mass will be said to be “heavy” and moving “down,” the small light and moving “up.” Now this is just what we ought to detect ourselves doing in our region here. Standing on the earth and detaching various earthy substances, and sometimes pure earth, we pull them into the dissimilar air by force and against nature, since both these kinds cleave to their own kindred; and the smaller mass yields more easily, and follows first, as we force it into the dissimilar kind; wherefore we name it “light,” and the region to which we force it “above”; and the conditions opposite thereto we name “heavy” and “below.” Thus, these must necessarily differ in their mutual relations, because the main masses of the Kinds occupy regions opposite to one another; for when we compare what is light in one region with what is light in the opposite region, and the heavy with the heavy, the “below” with the below, and the” above with the above, we shall discover that these all become and are opposite and oblique and in every way different in their mutual relations. There is, however, this one fact to be noticed about them all, that it is the passage of each kind to its kindred mass which makes the moving body heavy, and the region to which such a body moves “below”; while the opposite conditions produce the contrary results. Let this, then, stand as our account of the causes of these conditions.
ΤΙ. λείου δʼ αὖ καὶ τραχέος παθήματος αἰτίαν πᾶς που κατιδὼν καὶ ἑτέρῳ δυνατὸς ἂν εἴη λέγειν· σκληρότης γὰρ ἀνωμαλότητι μειχθεῖσα, τὸ δʼ ὁμαλότης πυκνότητι παρέχεται. μέγιστον δὲ καὶ λοιπὸν τῶν κοινῶν περὶ ὅλον τὸ σῶμα παθημάτων τὸ τῶν ἡδέων καὶ τῶν ἀλγεινῶν αἴτιον ἐν οἷς διεληλύθαμεν, καὶ ὅσα διὰ τῶν τοῦ σώματος μορίων αἰσθήσεις κεκτημένα καὶ λύπας ἐν αὑτοῖς ἡδονάς θʼ ἅμα ἑπομένας ἔχει. ὧδʼ οὖν κατὰ παντὸς αἰσθητοῦ καὶ ἀναισθήτου παθήματος τὰς αἰτίας λαμβάνωμεν, ἀναμιμνῃσκόμενοι τὸ τῆς εὐκινήτου τε καὶ δυσκινήτου φύσεως ὅτι διειλόμεθα ἐν τοῖς πρόσθεν· ταύτῃ γὰρ δὴ μεταδιωκτέον πάντα ὅσα ἐπινοοῦμεν ἑλεῖν. τὸ μὲν γὰρ κατὰ φύσιν εὐκίνητον, ὅταν καὶ βραχὺ πάθος εἰς αὐτὸ ἐμπίπτῃ, διαδίδωσιν κύκλῳ μόρια ἕτερα ἑτέροις ταὐτὸν ἀπεργαζόμενα, μέχριπερ ἂν ἐπὶ τὸ φρόνιμον ἐλθόντα ἐξαγγείλῃ τοῦ ποιήσαντος τὴν δύναμιν· τὸ δʼ ἐναντίον ἑδραῖον ὂν κατʼ οὐδένα τε κύκλον ἰὸν πάσχει μόνον, ἄλλο δὲ οὐ κινεῖ τῶν πλησίον, ὥστε οὐ διαδιδόντων μορίων μορίοις ἄλλων ἄλλοις τὸ πρῶτον πάθος ἐν αὐτοῖς ἀκίνητον εἰς τὸ πᾶν ζῷον γενόμενον ἀναίσθητον παρέσχεν τὸ παθόν. ταῦτα δὲ περί τε ὀστᾶ καὶ τὰς τρίχας ἐστὶν καὶ ὅσʼ ἄλλα γήϊνα τὸ πλεῖστον ἔχομεν ἐν ἡμῖν μόρια· τὰ δὲ ἔμπροσθεν περὶ τὰ τῆς ὄψεως καὶ ἀκοῆς μάλιστα, διὰ τὸ πυρὸς ἀέρος τε ἐν αὐτοῖς δύναμιν ἐνεῖναι μεγίστην. τὸ δὴ τῆς ἡδονῆς καὶ λύπης ὧδε δεῖ διανοεῖσθαι· τὸ μὲν παρὰ φύσιν καὶ βίαιον γιγνόμενον ἁθρόον παρʼ ἡμῖν πάθος ἀλγεινόν, τὸ δʼ εἰς φύσιν ἀπιὸν πάλιν ἁθρόον ἡδύ, τὸ δὲ ἡρέμα καὶ κατὰ σμικρὸν ἀναίσθητον, τὸ δʼ ἐναντίον τούτοις ἐναντίως. τὸ δὲ μετʼ εὐπετείας γιγνόμενον ἅπαν αἰσθητὸν μὲν ὅτι μάλιστα, λύπης δὲ καὶ ἡδονῆς οὐ μετέχον, οἷον τὰ περὶ τὴν ὄψιν αὐτὴν παθήματα, ἣ δὴ σῶμα ἐν τοῖς πρόσθεν ἐρρήθη καθʼ ἡμέραν συμφυὲς ἡμῶν γίγνεσθαι. ταύτῃ γὰρ τομαὶ μὲν καὶ καύσεις καὶ ὅσα ἄλλα πάσχει λύπας οὐκ ἐμποιοῦσιν, οὐδὲ ἡδονὰς πάλιν ἐπὶ ταὐτὸν ἀπιούσης εἶδος, μέγισται δὲ αἰσθήσεις καὶ σαφέσταται καθʼ ὅτι τʼ ἂν πάθῃ καὶ ὅσων ἂν αὐτή πῃ προσβαλοῦσα ἐφάπτηται· βία γὰρ τὸ πάμπαν οὐκ ἔνι τῇ διακρίσει τε αὐτῆς καὶ συγκρίσει.
Of “smoothness” and “roughness” anyone might be able to discern the causes and explain them also to others. For the cause of the latter is hardness combined with irregularity, and of the former regularity combined with density. In respect of the affections common to the whole body a very important point, which still remains, is the cause of the pleasures and pains attaching to the sense-affections we have been discussing; and the cause also of those affections which have become perceptible by means of the bodily parts and involve in themselves concomitant pains and pleasures. Let us, then, try to grasp the causes in connection with every perceptible and imperceptible affection in the following way, bearing in mind the distinction we previously drew between mobile and immobile substances; for it is in this way that we must track down all those facts that we intend to grasp. Whenever what is naturally mobile is impressed by even a small affection, it transmits it in a circle, the particles passing on to one another this identical impression until they reach the organ of intelligence and announce the quality of the agent. But a substance of the opposite kind, being stable and having no circular movement, is only affected in itself and does not move any other adjacent particle; consequently, since the particles do not transmit to one another the original affection, it fails to act upon the living creature as a whole, and the result is that the affected body is non-percipient. This is the case with the bones and the hair and all our other parts that are mainly earthy whereas the former character belongs especially to the organs of sight and of hearing, owing to the fact that they contain a very large quantity of fire and air. Now the nature of pleasure and pain we must conceive of in this way. When an affection which is against nature and violent occurs within us with intensity it is painful, whereas the return back to the natural condition, when intense, is pleasant; and an affection which is mild and gradual is imperceptible, while the converse is of a contrary character. And the affection which, in its entirety, takes place with ease is eminently perceptible, but it does not involve pain or pleasure; such, for example, are the affections of the visual stream itself, which, as we said before, becomes in the daylight a body substantially one with our own. For no pains are produced therein by cuttings or burnings or any other affections, nor does its reversion to its original form produce pleasures; but it has most intense and clear perceptions concerning every object that affects it, and every object also which it strikes against or touches; for force is wholly absent both from its dilation and from its contraction.
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